Method for calibrating semiconductor test instruments

ABSTRACT

A method for calibrating a semiconductor test instrument leading cost reduction, simplified work, and short working time. Drivers are related to comparators in one-to-one correspondence. A clock signal and a strobe signal have a one-to-one correspondence. The phase of either a clock signal or a strobe signal is adjusted with reference to the phase of the other signal. The relative phase difference between clock signals or between strobe signals are determined. The phases of the clock and strobe signals are adjusted with reference to the relative phase difference.

TECHNICAL FIELD

The present invention relates to a method for calibrating asemiconductor test instrument for adjusting operation timings of adriver and a comparator in pin electronics of the semiconductor testinstrument

BACKGROUND ART

The pin electronics of a semiconductor test instrument includes a driverfor applying a signal to a device under test and a comparator fordetermining the logic of a signal output from the device under testcorrespondingly to the signal. The driver outputs a signal synchronizingwith an input clock signal. Moreover, the comparator determinessynchronously with an input strobe signal.

In the initial state of the semiconductor test instrument, because thetime length of a signal route for each input/output pin of the deviceunder test fluctuates, the timing for outputting a signal from thedriver or the determination timing of the comparator shifts from anexpected timing. Therefore, timing calibration is applied to the deviceunder test before various tests are executed.

FIG. 73 is an illustration showing a conventional configuration of asemiconductor test instrument for performing timing calibration. In FIG.73, a semiconductor test instrument 90 is connected to a socket board 94through an exclusive cable 93 provided for a performance board 92. Forexample, to apply various tests to a device under test having a BGA(Ball Grid Array) type package, the socket board 94 on whose surfacemany pogo pins are provided. A test board 96 is used to simplify theoperation for bringing a probe 99 extended from a referencedriver/comparator (DR/CP) section 98 into contact with these pogo pinsprovided for the surface of the socket board 94 and has a structure inwhich pads provided for the surface and back are electrically connectedeach other.

FIG. 74 is an electrical layout diagram of the conventionalconfiguration shown in FIG. 73. The semiconductor test instrument 90 isprovided with a plurality of sets of drivers and comparators and eachset of a driver and a comparator is connected to a common device socketend through the performance board (PB) 92 and socket board (SB) 94. InFIG. 74, a test board 96 is omitted.

FIGS. 75, 76, and 77 are illustrations showing the outline ofconventional timing calibration. As shown in FIG. 75, phases (skews) ofclock signals CLK1 to CLKn and strobe signals STB1 to STBn input to ndrivers DR1 to DRn and n comparators CP1 to CPn respectively are shiftedin the initial state of a semiconductor test instrument.

First, the probe 99 of the reference driver/comparator section 98 isconnected to any device socket end through the test board 96 to make thephase of the strobe signal STB1 (timing of comparison by comparator CP1)coincide with the rise timing of a reference driver signal (referenceDR) (FIG. 76). Then, after the phase of a reference comparator signal(reference CP) is made to coincide with the rise timing of an outputsignal of the reference driver, the phase of the clock signal CLK1 inputto the driver DR1 is adjusted so that the rise timing of a signal outputfrom the driver DR1 coincides with the output timing of the referencecomparator signal (timing of comparison by reference comparator) (FIG.77). The above timing calibration operation is performed every devicesocket end.

Because the timing calibration method of the above conventionalsemiconductor test instrument performs timing correction at a devicesocket end, it is necessary to repeat movement of the probe 99 providedfor the reference driver/comparator section 98 and contact of the frontend of the probe 99. Therefore, to automate the above operation, aspecial apparatus is necessary. It is considered to make a robot performthe above operation. However, this type of the robot is generallyexpensive and it is not easy to handle the robot in order to secure ahigh optional accuracy in many cases. Therefore, there is a problem thatoperation contents are complicated. It is possible to manually align theprobe 99 without using a robot. However, when a device under test hasmany pins or there are many devices under test that are tested at thesame time, the number of times for repeating movement and contact of theprobe 99 greatly increases. Therefore, there is a problem that theworking time until timing calibration is completed increases.

DISCLOSURE OF THE INVENTION

The present invention is created to solve the above problems and itsobject is to provide a method for calibrating a semiconductor testinstrument capable of reducing the cost, simplifying operation contents,and shortening the working time.

A method of the present invention for calibrating a semiconductor testinstrument is constituted by including first to third steps in order toperform the timing calibration of a semiconductor test instrumentprovided with a driver for generating a signal synchronizing with aclock signal and a comparator for performing the comparisonsynchronizing with a strobe signal. In the first step, phases of one ofclock signals and strobe signals set in one-to-one correspondence areadjusted on the basis of the other while each of a plurality of driverscorresponds to each of a plurality of comparators. In the second step,relative phase differences between clock signals corresponding to aplurality of drivers respectively or relative phase differences betweenstrobe signals corresponding to a plurality of comparators respectivelyare obtained. In the third step, phases of a plurality of clock signalsand phases of a plurality of strobe signals are adjusted in accordancewith relative phase differences. Because an exclusive referencedriver/comparator section for performing only timing calibration, aprobe connected to the section, and an exclusive robot for automatingmovement and contact of a probe are unnecessary though they have beennecessary so far, it is possible to greatly reduce the cost.

Particularly, it is preferable to perform the phase adjustment to beexecuted in the above first step by varying the phase of a clock signalso that timings for performing comparisons by comparators in accordancewith strobe signals coincide with timings for changing signals outputfrom drivers and input to comparators. Or, it is preferable to performthe phase adjustment to be executed in the above first step by varyingphases of strobe signals so that timings for performing comparisons bycomparators in accordance with strobe signals coincide with timings forchanging signals output from drivers and input to comparators. Moreover,it is preferable to perform phase difference obtainment to be executedin the above second step by measuring the phase difference of either ofclock signals and strobe signals set in one-to-one correspondence on thebasis of the other signals while changing combinations of drivers withcomparators in the first step. By varying phases of clock signals orstrobe signals while observing results of comparisons by comparators, itis possible to easily adjust phases or measure relative phasedifferences.

Moreover, it is preferable to insert delay elements for varying phasesof signals into supply routes of clock signals to drivers and supplyroutes of strobe signals to comparators. By individually varying thedelay value of each delay element, it is possible to adjust the phase ofeach clock signal and strobe signal corresponding to each device socketend to an optional value.

Furthermore, it is preferable that the first step is executed by using afirst calibration board in which the output end of a correspondingdriver and the input end of a corresponding comparator are connected toeach short connection point through wirings having equal time lengths.Furthermore, it is preferable that the second step is executed by usinga second calibration board different in wiring combination from thefirst calibration board in which the output end of a correspondingdriver and the input end of a corresponding comparator are connected toeach short connection point through wirings having equal time lengths.It is possible to adjust phases of clock signals and strobe signals andmeasure phase differences of strobe signals or phase differences ofclock signals by using the first or second calibration board. Therefore,it is possible to simplify operation contents compared to a conventionalmethod in which the phase of a clock signal or probe signal is adjustedevery device socket end by using a probe.

Furthermore, it is preferable to include the fourth step of exchangingthe first calibration board with the second calibration board betweenthe first step and the second step. Because mechanical working includesonly exchange of the first calibration board with the second calibrationboard, it is possible to greatly shorten the working time in the wholetiming calibration.

Furthermore, it is preferable that the first step is executed by using athird calibration board in which the output end of a correspondingdriver and the input end of a corresponding comparator are connected toeach short connection point through wirings having equal time lengthsand the second step is executed by changing wiring states of the thirdcalibration board so that the output end of a corresponding driver andthe input end of a corresponding comparator are connected to each shortconnection point through wirings having equal time lengths. By using thethird calibration board capable of changing wiring contents, theexchange of calibration boards is unnecessary. Therefore, it is possibleto further shorten the whole working time.

Furthermore, because a plurality of changeover switches for changingwiring states is included in the third calibration board, it ispreferable to perform operations in the first and second steps bychanging connection states of these switches. Thereby, it is possible toeasily change wiring states of the third calibration board.

Furthermore, instead of using the above various calibration boards, itis allowed to use a calibration device or calibration wafer in which thesame wiring is made. Particularly, by exchanging calibration devices byusing a handler, it is possible to automate the exchanging operation.

Furthermore, a method of the present invention for calibrating asemiconductor test instrument is constituted by including the first tothird steps in order to perform the timing calibration of thesemiconductor test instrument provided with a driver for generating asignal synchronizing with a clock signal and a comparator for performingthe comparison synchronizing with a strobe signal. In the first step,phases of a clock signal and a strobe signal are adjusted by makingtimings for changing signals output from a plurality of drivers andinput to a plurality of comparators coincide with timings for performingcomparisons by a plurality of comparators every group when the driversand the comparators are divided into m number of groups so that two ormore drivers or comparators are included. In the second step, relativephase differences of clock signals corresponding to the drivers orrelative phase differences of strobe signals corresponding to thecomparators are obtained for different groups. In the third step, phasesof clock signals corresponding to drivers and phases of strobe signalscorresponding to comparators included in a plurality of groups areadjusted in accordance with relative phase differences. Because anexclusive reference driver/comparator section for performing only timingcalibration, a probe connected to the section, and an exclusive robotfor automating movement and contact of the probe are unnecessary thoughthey have been necessary so far, it is possible to greatly reduce thecost. Moreover, by performing calibration every group, it is possible toaverage adjustment errors in the group. Therefore, it is possible toreduce calibration errors caused by fluctuation of measurement results.

Furthermore, it is preferable to insert a delay element for varying thephase of a signal into each of supply routes of clock signals to thedrivers and each of supply routes of strobe signals to the comparators.By individually varying the delay value of each delay element, it ispossible to adjust phases of a clock signal and a strobe signal tooptional values and thereby, it is simplified to adjust phases of thesesignals.

Furthermore, it is preferable that the first step is executed by using afirst calibration board in which the output end of a driver and theinput end of a comparator are connected each other through a firstcommon short connection point for each of groups. Furthermore, it ispreferable that the second step is executed by using a secondcalibration board in which the output end of a driver included in onegroup and the input end of a comparator included in the other group areconnected each other through a second common connection point. Becausecalibration is performed by exchanging the first calibration board withthe second calibration board, it is possible to simplify workingcontents compared to a conventional method for individually adjustingphases of a clock signal and a strobe signal by using a probe.

Furthermore, it is preferable to equally set the length of the wiringfor connecting the driver with the first and second short connectionpoints and the length of the wiring for connecting the comparator withthe first and second short connection points. Thereby, it is possible toadjust every clock signal and strobe signal under the same condition andrealize calibration by observing the output of a comparator.

Furthermore, it is preferable to include a fourth step of changing thefirst calibration board to the second calibration board between thefirst and second steps. Because mechanical working includes onlyexchange of the first calibration board with the second calibrationboard, it is possible to greatly shorten the working time in the wholetiming calibration.

Furthermore, it is preferable that the first step is executed by using athird calibration board in which the output end of a driver and theinput end of a comparator included in each group are connected throughwirings having equal time lengths for every group and the second step isexecuted by changing wiring states of the third calibration board sothat the output end of a driver included in one group and the input endof a comparator included in the other group are connected each otherthrough wirings having equal time lengths. By using the thirdcalibration board capable of changing wiring contents, it is unnecessaryto exchange calibration boards and thereby it is possible to furthershorten the whole working time.

Furthermore, because a plurality of changeover switches for changingwiring states is included in the third calibration board, it ispreferable to perform operations in the first and second steps bychanging connection states of these switches. Thereby, it is possible toeasily change wiring states of the third calibration board.

Furthermore, instead of using the above various calibration boards, itis allowed to use a calibration device or calibration wafer in which thesame wiring is made. Particularly, by exchanging calibration devices byusing a handler, it is possible to automate the exchanging operation.

Furthermore, a method of the present invention for calibrating asemiconductor test instrument is constituted by including first to thirdsteps in order to perform the timing calibration of the semiconductortest instrument provided with a driver for generating a signalsynchronizing with a clock signal and a comparator for performing thecomparison synchronizing with a strobe signal. In the first step, whilea plurality of drivers and a plurality of comparators are divided into mnumber of groups so that two or more drivers or comparators areincluded, the phase of a clock signal corresponding to an in-groupcommon driver included in each group is adjusted on the basis of astrobe signal corresponding to a comparator serving as a commoncomparator. In the second step, phases of strobe signals correspondingto comparators included in the same group are adjusted on the basis of aclock signal corresponding to the in-group common driver in each of mnumber of groups. In the third step, phases of clock signalscorresponding to drivers included in the same group are adjusted on thebasis of the phase of a strobe signal corresponding to an optionalcomparator in each of m number of groups.

Or, a method of the present invention for calibrating a semiconductortest instrument is constituted by including first to third steps inorder to perform the timing calibration of the semiconductor testinstrument provided with a driver for generating a signal synchronizingwith a clock signal and a comparator for performing the comparisonsynchronizing with a strobe signal. In the first step, while a pluralityof drivers and a plurality of comparators are divided into m number ofgroups so that two or more drivers or comparators are included, thephase of a strobe signal corresponding to an in-group common comparatorincluded in each group is adjusted on the basis of a clock signalcorresponding to a driver serving as a common driver. In the secondstep, phases of clock signals corresponding to drivers included in thesame group are adjusted on the basis of a strobe signal corresponding toan in-group common comparator in each of m number of groups. In thethird step, phases of strobe signals corresponding to comparatorsincluded in the same group are adjusted on the basis of the phase of aclock signal corresponding to an optional driver in each of m number ofgroups.

Because an exclusive reference driver/comparator section for performingonly timing calibration, a probe connected to the section, and anexclusive robot for automating movement and contact of the probe areunnecessary though they have been necessary so far, it is possible togreatly reduce the cost. Moreover, because adjustments in the second andthird steps can be performed in parallel every group, it is possibleimprove the working efficiency and shorten the working time.

It is preferable to perform the adjustment of a phase to be executed ineach of the first to third steps by varying the phase of a clock signalor strobe signal so that the timing for performing comparison by acomparator in accordance with a strobe signal coincides with the timingfor changing a signal output from each driver and input to eachcomparator. By varying the phase of a clock signal or strobe signalwhile observing a result of the comparison by a comparator, it ispossible to easily adjust these phases and measure relative phasedifferences.

Moreover, it is preferable that a delay element for varying the phase ofa signal is inserted into the supply route of a clock signal to thedriver and that of a strobe signal to the comparator. By individuallyvarying the delay value of each delay element, it is possible to adjustphases of a clock signal and a strobe signal to optional values and thephasing of these signals is simplified.

Furthermore, it is preferable that the first step is executed by using afirst calibration board in which the input end of a common comparatorand the output end of an in-group common driver are connected each otherthrough a first common short connection point. Or, it is preferable thatthe first step is executed by using a first calibration board in whichthe output end of the common driver and the input end of an in-groupcommon comparator are connected each other through the first commonconnection point. Moreover, it is preferable that the second and thirdsteps are executed by using a second calibration board in which theoutput end of a driver and the input end of a comparator are connectedeach other through a second common short connection point for each ofgroups. Because calibration is performed by exchanging the firstcalibration board with the second calibration board, it is possible tosimplify working contents compared to a conventional method forindividually adjusting phases of a clock signal and strobe signal byusing a probe.

Furthermore, it is preferable to set the length of a wiring forconnecting the driver with the first and second short connection pointsand the length of a wiring for connecting the comparator with the firstand second short connection points so that the lengths are allequalized. Thereby, it is possible to adjust every clock signal andstrobe signal under the same condition and thereby, calibration isrealized by observing an output of a comparator.

Furthermore, it is preferable to include a fourth step of exchanging thefirst calibration board with the second calibration board between thefirst and second steps. Because mechanical working includes onlyexchange of the first calibration board with the second calibrationboard, it is possible to greatly shorten the working time in the wholetiming calibration.

Furthermore, it is preferable that the first step is executed by using athird calibration board in which the input end of a common comparatorand the output end of an in-group common driver included in each of mnumber of groups are connected each other through wiring having equaltime lengths for all groups and the second and third steps are executedby changing wiring states of the third calibration board so that theoutput end of a driver and the input end of a comparator included ineach group are connected each other through wirings having equal timelengths for all groups. Or, it is preferable that the first step isexecuted by using the third calibration board in which the output end ofa common driver and the input end of an in-group common comparatorincluded in each of m number of groups are connected each other throughwirings having equal time lengths for all groups and the second andthird steps are executed by changing wiring states of the thirdcalibration board so that the output end of a driver and the input endof a comparator included in each group are connected each other throughwirings having equal time lengths for all groups. By using the thirdcalibration board capable of changing wiring states, exchange ofcalibration boards is unnecessary. Therefore, it is possible to furthershorten the whole working time.

Furthermore, because a plurality of changeover switches for changingwiring states is included in the third calibration board, it ispreferable to perform operations in the first, second, and third stepsby changing connection states of these changeover switches. Thereby, itis possible to easily change wiring states of the third calibrationboard.

Furthermore, instead of using the above various calibration boards, itis also allowed to use a calibration device or calibration wafer inwhich the same wiring is made. Particularly, by exchanging calibrationdevices by using a handler, it is possible to automate the exchangingoperation.

Furthermore, a method of the present invention for calibration asemiconductor test instrument is constituted by including first andsecond steps in order to perform the timing calibration of thesemiconductor test instrument provided with a driver for generating asignal synchronizing with a clock signal and a comparator for performingthe comparison synchronizing with a strobe signal. In the first step,the phase of a strobe signal corresponding to each of a plurality ofcomparators is adjusted on the basis of a clock signal corresponding toa driver. In the second step, the phase of a clock signal correspondingto each of a plurality of drivers is adjusted on the basis of a strobesignal whose phase adjustment is completed in the first step.

Or, a method of the present invention for calibrating a semiconductortest instrument is constituted by including first and second steps inorder to perform the timing calibration of the semiconductor testinstrument provided with a driver for generating a signal synchronizingwith a clock signal and a comparator for performing the comparisonsynchronizing with a strobe signal. In the first step, the phase of aclock signal corresponding to each of a plurality of drivers is adjustedon the basis of a strobe signal corresponding to a comparator. In thesecond step, the phase of a strobe signal corresponding to each of aplurality of comparators is adjusted on the basis of a clock signalwhose phase adjustment is completed in the first step.

Because an exclusive reference driver/comparator section for performingonly timing calibration, a probe connected to the section, and anexclusive robot for automating movement and contact of the probe areunnecessary, it is possible to greatly reduce the cost.

Moreover, it is preferable to perform adjustments of phases to beexecuted in the first and second steps by varying the phase of a clocksignal or strobe signal so that the timing for performing comparison bya comparator in accordance with the strobe signal coincides with thetiming for changing a signal output from each driver and input to eachcomparator. By varying the phase of the clock signal or strobe signalwhile observing a result of the comparison by the comparator, it ispossible to easily adjust these phases and measure relative phasedifferences.

Furthermore, it is preferable that a delay element for varying the phaseof a signal is inserted into the supply route of a clock signal to thedriver and that of a strobe signal to the comparator. By individuallyvarying the delay value of each delay element, it is possible to adjustphases of a clock signal and strobe signal to optional values and thephasing of these signals is simplified.

Furthermore, it is preferable that the first step is executed by using aplurality of first calibration boards in which the output end of adriver and the input end of each of a plurality of comparators areseparately connected each other through a first short connection point.Or, it is preferable that the first step is executed by a plurality offirst calibration boards in which the output end of each of a pluralityof drivers and the input end of a comparator are separately connectedeach other through the first short connection point. Moreover, it ispreferable that the second step is executed by using a secondcalibration board in which each of a plurality of drivers corresponds toeach of a plurality of comparators and the output end of a correspondingdriver and the input end of a corresponding comparator are connectedeach other. Because calibration is performed by exchanging the firstcalibration board with the second calibration board, it is possible tosimplify working contents compared to a conventional method in whichphases of a clock signal and strobe signal are individually adjusted bya probe.

Furthermore, it is preferable to set the length of a wiring forconnecting the driver with the first and second short connection pointsand the length of a wiring for connecting the comparator with the firstand second short connection points so that the lengths are equalized.Thereby, it is possible to adjust every clock signal and strobe signalunder the same condition and realize the calibration by observing anoutput of the comparator.

Furthermore, instead of using the above various calibration boards, itis also allowed to use a calibration device or calibration wafer inwhich the same wiring is made. Particularly, by exchanging calibrationdevices by using a handler, it is possible to automate the exchangingoperation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration showing a general configuration of asemiconductor test instrument to which timing calibration will beapplied;

FIG. 2 is an illustration showing a wiring state of one calibrationboard;

FIG. 3 is an illustration showing a wiring state of the othercalibration board;

FIG. 4 is a flow chart showing a calibration procedure of a firstembodiment;

FIG. 5 is an illustration showing a state in which one calibration board(CB) is set to a semiconductor test instrument;

FIG. 6 is an illustration showing the outline of the clock signalphasing to be executed in step 101;

FIG. 7 is an illustration showing details of the adjustment of phases ofclock signals shown in FIG. 6;

FIG. 8 is an illustration showing a state in which the other calibrationboard is set to the semiconductor test instrument;

FIG. 9 is an illustration showing the outline of the strobe signal phasedifference obtainment to be executed in step 103;

FIG. 10 is an illustration showing outlines of the strobe signalcorrection value decision and strobe signal correction to be executed insteps 104 and 105;

FIG. 11 is an illustration showing the outline of the clock signal phasecorrection to be executed in step 106;

FIG. 12 is an illustration showing a configuration of a calibrationboard of a second embodiment having functions of two types ofcalibration boards different from each other in wiring contents;

FIG. 13 is an illustration showing a configuration of the secondembodiment having functions of two types of calibration boards differentfrom each other in wiring contents;

FIG. 14 is an illustration showing a wiring state of one calibrationboard used to perform calibration in a third embodiment;

FIG. 15 is an illustration showing a wiring state of the othercalibration board used to perform calibration in the third embodiment;

FIG. 16 is an illustration showing initial states of a clock signal anda strobe signal in a semiconductor test instrument before performingcalibration;

FIG. 17 is a flow chart showing a calibration procedure of the thirdembodiment;

FIG. 18 is an illustration showing drivers and comparators to or fromwhich signals are input or output correspondingly to step 201 shown inFIG. 17;

FIG. 19 is an illustration showing the outline of the strobe signalphase adjustment to be executed in step 201 in FIG. 17;

FIG. 20 is an illustration showing drivers and comparators to or fromwhich signals are input or output correspondingly to step 202 shown inFIG. 17;

FIG. 21 is an illustration showing the outline of the clock signal phaseadjustment to be executed in step 202 shown in FIG. 17;

FIG. 22 is an illustration showing a driver and a comparator to or fromwhich signals are input or output correspondingly to step 204 shown inFIG. 17;

FIG. 23 is an illustration showing the outline of the strobe signalphase difference measurement to be executed in step 204 shown in FIG.17;

FIG. 24 is an illustration showing the outline of the strobe signalphase correction to be executed in step 206 shown in FIG. 17;

FIG. 25 is an illustration showing drivers and comparators to or fromwhich signals are input or output correspondingly to step 207 shown inFIG. 17;

FIG. 26 is an illustration showing the outline of the clock signalcorrection to be executed in step 207 shown in FIG. 17;

FIG. 27 is an illustration showing a configuration of a calibrationboard of a fourth embodiment having functions of two types ofcalibration boards different from each other in wiring contents;

FIG. 28 is an illustration showing a configuration of a calibrationboard of the fourth embodiment having functions of two types ofcalibration boards different from each other in wiring contents;

FIG. 29 is an illustration showing a wiring state of one calibrationboard of a fifth embodiment;

FIG. 30 is an illustration showing a wiring state of the othercalibration board of the fifth embodiment;

FIG. 31 is a flow chart showing a calibration procedure of the fifthembodiment;

FIG. 32 is an illustration showing a driver and a comparator to or fromwhich signals are input or output correspondingly to step 301 shown inFIG. 31;

FIG. 33 is an illustration showing the outline of the clock signal phaseadjustment to be executed in step 301 shown in FIG. 31;

FIG. 34 is an illustration showing drivers and comparators to or fromwhich signals are input or output correspondingly to step 303 shown inFIG. 31;

FIG. 35 is an illustration showing the outline of the strobe signalphase adjustment to be executed in step 303 shown in FIG. 31;

FIG. 36 is an illustration showing drivers and comparators to or fromwhich signals are input or output correspondingly to step 304 shown inFIG. 31;

FIG. 37 is an illustration showing the outline of the clock signal phaseadjustment to be executed in step 304 shown in FIG. 31;

FIG. 38 is an illustration showing a configuration of one calibrationboard of a sixth embodiment;

FIG. 39 is a flow chart showing a calibration procedure of the sixthembodiment;

FIG. 40 is an illustration showing a configuration of a calibrationboard of a seventh embodiment having functions of two types ofcalibration boards different from each other in wiring contents;

FIG. 41 is an illustration showing a configuration of a calibrationboard of the seventh embodiment having functions of two types ofcalibration boards different from each other in wiring contents;

FIG. 42 is an illustration showing a configuration of a calibrationboard of a modification having functions of two types of calibrationboards different from each other in wiring contents;

FIG. 43 is an illustration showing a configuration of a calibrationboard of a modification having functions of two types of calibrationboards different from each other in wiring contents;

FIG. 44 is an illustration showing a wiring state of a calibration boardused for a calibration method of an eighth embodiment;

FIG. 45 is an illustration showing a wiring state of a calibration boardused for the calibration method of the eighth embodiment;

FIG. 46 is an illustration showing a wiring state of a calibration boardused for the calibration method of the eighth embodiment;

FIG. 47 is an illustration showing a wiring state of a calibration boardused for the calibration method of the eighth embodiment;

FIG. 48 is an illustration showing a wiring state of a calibration boardused for the calibration method of the eighth embodiment;

FIG. 49 is a flow chart showing a calibration procedure of the eighthembodiment;

FIG. 50 is an illustration showing a modification of a calibration boardof the eighth embodiment;

FIG. 51 is an illustration showing a configuration of a calibrationboard of a ninth embodiment having functions of n+1 types of calibrationboards different from each other in wiring contents;

FIG. 52 is an illustration showing a modification of the calibrationboard shown in FIG. 51;

FIG. 53 is an illustration showing a modification in which the settingstate of a calibration board is changed;

FIG. 54 is an illustration of the clock signal phase adjustmentcorresponding to the configuration shown in FIG. 53;

FIG. 55 is an illustration showing a connection state between acalibration device and a semiconductor test instrument;

FIG. 56 is an illustration showing the outline of the timing calibrationusing a calibration device;

FIG. 57 is an illustration showing a connection state between acalibration wafer and a semiconductor test instrument;

FIG. 58 is an illustration showing the outline of the timing calibrationusing a calibration wafer;

FIG. 59 is an illustration showing a calibration device realizing thesame wiring state as the case of the calibration board used for thefirst embodiment;

FIG. 60 is an illustration showing a calibration device realizing thesame wiring state as the case of a calibration board used for the firstembodiment;

FIG. 61 is an illustration showing a calibration device realizing thesame wiring state as the case of the calibration board used for thethird embodiment;

FIG. 62 is an illustration showing a calibration device realizing thesame wiring state as the case of the calibration board used for thethird embodiment;

FIG. 63 is an illustration showing a calibration device realizing thesame wiring state as the case of the calibration board used for thefifth embodiment;

FIG. 64 is an illustration showing a calibration device realizing thesame wiring state as the case of the calibration board used for theeighth embodiment;

FIG. 65 is an illustration showing a calibration device realizing thesame wiring state as the case of the calibration board used for theeighth embodiment;

FIG. 66 is an illustration showing a calibration device realizing thesame wiring state as the case of the calibration board used for theeighth embodiment;

FIG. 67 is an illustration showing a calibration device realizing thesame wiring state as the case of the calibration board used for theeighth embodiment;

FIG. 68 is an illustration showing a calibration device realizing thesame wiring state as the case of the calibration board used for theeighth embodiment;

FIG. 69 is an illustration showing a calibration wafer realizing thesame wiring state as the case of the calibration boards used for thefirst embodiment;

FIG. 70 is an illustration showing a calibration wafer realizing thesame wiring state as the case of the calibration board used for thethird embodiment;

FIG. 71 is an illustration showing a calibration wafer realizing thesame wiring state as the case of the calibration board used for thefifth embodiment;

FIG. 72 is an illustration showing a calibration wafer realizing thesame wiring state as the case of the calibration board used for theeighth embodiment;

FIG. 73 is an illustration showing a conventional configuration forperforming the timing calibration of a semiconductor test instrument;

FIG. 74 is an electrical layout diagram of the conventionalconfiguration shown in FIG. 73;

FIG. 75 is an illustration showing the outline of conventional timingcalibration;

FIG. 76 is an illustration showing the outline of conventional timingcalibration; and

FIG. 77 is an illustration showing the outline of conventional timingcalibration.

BEST MODE FOR CARRYING OUT THE INVENTION

A method of an embodiment providing the present invention forcalibrating a semiconductor test instrument is described below indetail.

[First Embodiment]

FIG. 1 is an illustration showing a general configuration of asemiconductor test instrument to which the timing calibration performedin the first embodiment will be applied. The semiconductor testinstrument is constituted by including a semiconductor test instrument10 and a work station (WS) 40 in order to apply a predetermined test toa device under test (DUT) (not illustrated).

The work station 40 controls a series of test operations such as afunctional test and the whole timing calibration and realizes aninterface with users.

The semiconductor test instrument 10 applies various tests to a DUT byexecuting a predetermined test program transferred from the work station40. Moreover, the semiconductor test instrument 10 performs timingcalibration by executing an exclusive program transferred from the workstation 40. To execute the above operations, the semiconductor testinstrument 10 has a tester control section (TP) 12, a timing generator(TG) 14, a pattern generator (PG) 16, a data selector (DS) 18, a formatcontrol section (FC) 20, and a pin electronics 22.

The tester control section 12 is connected with component sections ofthe timing generator 14 or the like through a bus to perform the controlnecessary for various test operations and calibrations for the componentsections.

The timing generator 14 sets a basic cycle of test operations andgenerates various timing edges included in the basic cycle. The patterngenerator 16 generates pattern data to be input to each pin of a DUT.The data selector 18 relates various pattern data values output from thepattern generator 16 with pins of the DUT for receiving the variouspattern data values. The format control section 20 controls waveforms ofthe DUT in accordance with the pattern data generated by the patterngenerator 16 and selected by the data selector 18 and the timing edgegenerated by the timing generator 14.

The pin electronics 22 forms a physical interface between the pinelectronics 22 and the DUT and generates signals to be transferredactually to and from the DUT in accordance with a clock signal CLK orstrobe signal STB generated through the waveform control by the formatcontrol section 20. To execute the above operations, the pin electronics22 is constituted by including n drivers DR1 to DRn and n comparatorsCP1 to CPn.

The driver DR1 generates a signal synchronizing with a clock signal CLK1and changes an output signal from low level to high level when the clocksignal CLK1 rises. Similarly, the drivers DR2 to DRn generate signalssynchronizing with input clock signals CLK2 to CLKn and respectivelychange an output signal from low level to high level when acorresponding clock signal rises.

In the case of not only this embodiment but also other embodiments, anoutput signal of a driver changes the same as the case of a clocksignal, that is, the output signal of the driver rises synchronouslywith the rise of the clock signal and falls synchronously with the fallof the clock signal. However, it is also allowed that the output signalof the driver falls synchronously with the rise of the clock signal andrises synchronously with the fall of the clock signal.

The comparator CP1 performs the comparison synchronizing with a strobesignal STBL output from the format control section 20 and determines thelogic of a signal input from a corresponding pin of the DUT when thestrobe signal STB1 is input. Similarly, the comparators CP2 to CPnperform comparisons synchronizing with input strobe signals STB2 to STBnand respectively determine the logic of a signal input from acorresponding pin of the DUT when a corresponding strobe signal isinput.

To perform the comparison synchronizing with a strobe signal by acomparator, the following cases are considered: a case of performingcomparison by a comparator synchronously with the rise of a strobesignal and a case of performing comparison by the comparatorsynchronously with the fall of the strobe signal. In the case of notonly this embodiment but also other embodiments, it is allowed to useeither of comparison timings because there is no essential difference inthe relation with the present invention.

The above driver DR1 and comparator CP1 correspond to one input/outputpin of the DUT as one set. Moreover, the driver DR2 and comparator CP2correspond to another input/output pin as one set. Thus, a set of adriver and a comparator is provided by relating them to eachinput/output pin of the DUT.

Furthermore, a performance board 30 is mounted on the semiconductor testinstrument 10 and the above pin electronics 22 is connected to acalibration board 50A (or 50B) through the performance board 30.

Special internal wirings different from each other are applied to thecalibration boards 50A and 50B in order to perform timing calibration.

FIG. 2 is an illustration showing a wiring state of the calibrationboard 50A. In FIG. 2, two terminals 1 a and 1 b are connected with ashort connection point (device socket end) 1 c in common and moreover,set so that their wiring lengths (time lengths) in terms of signal delaytime are equalized. Moreover, two terminals 2 a and 2 b are connectedwith a short connection point 2 c in common and moreover, set so thattheir wiring lengths in terms of signal delay time are equalized.Furthermore, two terminals na and nb are connected with a shortconnection point nc in common and set so that their wiring lengths interms of signal delay time are equalized. Furthermore, the above wiringlengths are equally set for all short connection points.

FIG. 3 is an illustration showing a wiring state of the othercalibration board 50B. In FIG. 3, two terminals 1 a and nb are connectedwith the short connection point 1 c in common and set so that theirwiring lengths in terms of signal delay time are equalized. Moreover,two terminals 2 a and 1 b are connected with the short connection point2 c in common and set so that their wiring lengths in terms of signaldelay time are equalized. Furthermore, two terminals na and 2 b areconnected with the short connection point nc in common and set so thattheir wiring lengths in terms of signal delay time are equalized.Furthermore, the above wiring lengths are equally set for all shortconnection points of two types of calibration boards 50A and 50B.

A semiconductor test instrument of the present invention has the aboveconfiguration and the calibration using the instrument is describedbelow.

FIG. 4 is a flow chart showing a calibration procedure of thisembodiment. After one calibration board 50A is set to the performanceboard 30 (step 10), the tester control section 12 adjusts the phase of aclock signal on the basis of a strobe signal every short connectionpoint of the calibration board 50A (step 101).

In the above step 101, the phase adjustment of a clock signal isperformed by observing the level of an output signal when a strobesignal is output (raised) and comparison is performed by a comparatorwhile changing the rise timing of a clock signal little by little andobtaining the phase of the clock signal when the level of the outputsignal of the comparator is just inverted.

FIG. 5 is an illustration showing a state in which the calibration board(CB) 50A is set to the semiconductor test instrument 10 through theperformance board (PB) 30. In FIG. 5, Tx1 to Txn respectively denote adelay time caused by a wiring from the output end of each driver up to aterminal of the calibration board 50A, Ty1 to Tyn respectively denote adelay time caused by a wiring from a terminal of the calibration board50A up to the input end of each comparator, and Ta denotes a delay timecaused by each wiring in the calibration board 50A. For example, it isassumed that Tx1 to Txn and Ty1 to Tyn are all set to the same value.

As shown in FIG. 5, a delay element T is set to routes through which aclock signal is supplied to the drivers DR1 to DRn in order to adjustthe phase (change timing) of the clock signal. By varying the elementconstant of each delay element, it is possible to optionally andindependently adjust phases of clock signals to the drivers DR1 to DRn.Similarly, a delay element T is set to routes through which a strobesignal is supplied to the comparators CP1 to CPn in order to adjust thephase of the strobe signal. By varying element constants of the delayelements T, it is possible to optionally and independently adjust thephase of the strobe signal to the comparators CP1 to CPn.

For this embodiment and embodiments from the second embodiment downward,a case is described in which wiring lengths from terminals of acalibration board up to the output end of a driver and the input end ofa comparator are equally set. However, it is also allowed todifferentiate these wiring lengths and adjust differences between thewiring lengths by the above delay element T.

FIG. 6 is an illustration showing the outline of the clock signal phaseadjustment to be executed in the above step 101. Moreover, FIG. 7 is anillustration showing details of the clock signal phase adjustment shownin FIG. 6. In FIG. 7, “DR”, “short connection point”, and “CP” showncorrespondingly to each clock signal respectively denote the timing atwhich a signal output from a driver correspondingly to each clock signalpasses or arrives. When noticing the clock signal CLK1, a signal isoutput from the driver DR1 correspondingly to the clock signal CLK1 atthe timing shown by “DR”. This signal arrives at a short connectionpoint (device socket end) at the timing shown by “short connectionpoint” and moreover, arrives at the comparator CP1 at the timing shownby “CP”. FIG. 6 notices the timing shown by “CP” in FIG. 7 and omitsother portions.

First, the tester control section 12 notices the short connection point1 c, fixes the phase (timing for comparison) of the strobe signal STB1input to the converter CP1, thereby varies the phase of the clock signalCLK1 input to the driver DR1, and thus adjusts a signal output from thedriver DR1 correspondingly to the clock signal CLK1 so that the signalrises when it is input to the comparator CP1 via the short connectionpoint 1 c and terminal 1 b. Then, the tester control section 12 noticesthe short connection point 2 c, fixes the phase (timing for comparison)of the strobe signal STB2 input to the comparator CP2, thereby variesthe phase of the clock signal CLK2 input to the driver DR2, and thusadjusts a signal output from the driver DR2 correspondingly to the clocksignal CK2 so that the signal rises when it is input to the comparatorCP2 via the short connection point 2 c and terminal 2 b. Thus, thetester control section 12 notices each of short connection points up tothe short connection point nc, fixes the phase (timing for comparison)of the strobe signal STBi (i=1,2, . . . , n) input to a comparator CPi,thereby varies the phase of the clock signal CLKi input to a driver DRi,and thus adjusts a signal output from a driver DRi correspondingly tothe clock signal CLKi so that the signal rises when it is input to thecomparator CPi via a short connection point ic and terminal ib.

Thus, when the phase adjustment of the clock signals CLK1 to CLKncorresponding to all the short connection pints 1 c to nc is completedby using one calibration board 50A, the other calibration board 50B isset (step 102). It is considered to set the calibration boards 50A and50B manually or by using an exclusive robot in order to automate theworking in steps 100 and 102.

FIG. 8 is an illustration showing a state in which the calibration board50B is set to the semiconductor test instrument 10.

Then, the tester control section 12 obtains phase differences of strobesignals through measurement every short connection point (step 103).

FIG. 9 is an illustration showing the outline of the strobe signal phasedifference obtainment to be executed in step 103. First, the testercontrol section 12 notices the short connection point 1 c of thecalibration board 50B to measure the phase difference Tn of the strobesignal STBn input to the comparator CPn on the basis of the phase of theclock signal CLK1 input to the driver DR1 (more accurately, on the basisof the timing at which a signal output from the driver DR1correspondingly to the clock signal CLK1 rises at the input end of thecomparator CPn). The above measurement can be performed by scanning thephase of the strobe signal STBn in a predetermined range while fixingthe phase of the clock signal CLK1. Specifically, the output timing ofthe strobe signal STBn is changed little by little until the level of anoutput signal of the comparator CPn is inverted while the rise timing ofa signal output from the driver DR1 correspondingly to the clock signalCLK1 and input to the comparator CPn via the short connection point 1 c.Thus, a change value when changing the phase of the strobe signal STBncorresponds to the phase difference Tn of the strobe signal STBn to bemeasured.

Then, the tester control section 12 notices the short connection point 2c of the calibration board 50B to measure the phase difference T1 of thestrobe signal STB1 input to the comparator CP1 on the basis of the phaseof the clock signal CLK2 input to the driver DR2. Thus, the testercontrol section 12 notices each of short connection points up to theshort connection point nc of the calibration board 50B to measure thephase difference Tj (j=n, 1, 2, . . . , n−1) of a strobe signal STBjinput to a comparator CPj on the basis of the phase of a clock signalCLKi (i=1,2, . . . n) input to each driver DRi corresponding to the nextset.

Thus, by using the other calibration board 50B, relative phasedifferences of all strobe signals STB1 to STBn are obtained.

Then, the tester control section 12 decides a correction value of astrobe signal by using phase differences of the strobe signals STB1 toSTBn (step 104). Specifically, in the case of obtainment of phasedifferences of strobe signals in step 103, a relative displacementbetween phases of two strobe signals input to two comparatorscorresponding to two adjacent short connection points respectively canbe known. Therefore, by using the phase of a strobe signal input to acomparator corresponding to a certain short connection point as acriterion, it is possible to decide a correction value necessary toadjust the phase of a strobe signal input to another comparator to thephase of the strobe signal serving as the criterion. Thereafter, thetester control section 12 corrects phases of the strobe signals STB1 toSTBn input to the comparators CP1 to CPn by using the decided correctionvalue (step 105).

FIG. 10 is an illustration showing the outline of the strobe signalcorrection value decision and strobe signal correction to be executed insteps 104 and 105. For example, when the phase difference of the strobesignal STB2 is T1 when using the phase (output timing) of the strobesignal STB1 as a criterion, the tester control section 12 adjusts thephase of the strobe signal STB2 to the phase of the strobe signal STB1by shifting the phase of the strobe signal STB2 by T1. Thereby, it ispossible to adjust the timing of the comparison by the comparator CP1synchronizing with the strobe signal STB1 to the timing of thecomparison by the comparator CP2 synchronizing with the strobe signalSTB2.

Moreover, when the phase difference of the strobe signal STBn is T1+T2when using the phase (output timing) of the strobe signal STB1 as acriterion, the tester control section 12 adjusts the phase of the strobesignal STBn to the phase of the strobe signal STB1 by shifting the phaseof the strobe signal STBn by T1+T2. Thus, it is possible to make timingsof comparisons by all comparators coincide with each other.

Then, the tester control section 12 corrects phases of the clock signalsCLK1 to CLKn input to the drivers DR1 to DRn respectively (step 106).This correction is performed by using the correction value of a strobesignal input to a comparator corresponding to each driver.

FIG. 11 is an illustration showing the outline of the clock signalcorrection to be executed in step 106. First, the tester control section12 corrects the phase of the clock signal CLK2 corresponding to thestrobe signal STB2 whose correction is completed in step 105 so as tocoincide with the phase of the strobe signal STB2. Moreover, the testercontrol section 12 corrects phases of corresponding clock signals up tothe clock signal CLKn so as to coincide with phases of strobe signals upto the strobe signal STBn. Thus, it is possible to make the timings atwhich signals output from drivers rise synchronously with rises of clocksignals coincide with each other.

Thus, in the case of the semiconductor test instrument of thisembodiment, the phase of a clock signal is first adjusted on the basisof a strobe signal every socket device end by using one calibrationboard 50A. Then, by using the other calibration board 50B, thedifference between phases of two strobe signals at adjacent shortconnection points is measured and then, the phase of any strobe signalor clock signal is corrected on the basis of a clock signal or strobesignal corresponding to any short correction point. Therefore, in thecase of the calibration by the semiconductor test instrument of thisembodiment, it is not necessary to bring a probe into contact with anobject every short connection point but it is only necessary to set thecalibration boards 50A and 50B. Therefore, it is possible to simply theworking contents necessary for calibration. Moreover, it is unnecessaryto use a special configuration including another referencedriver/comparator section and an exclusive robot for repeating contactor movement of a probe and thus, it is possible to greatly reduce thecost. Furthermore, because an operation followed by a mechanicalmovement before calibration is completed is only setting of thecalibration boards 50A and 50B, it is possible to greatly shorten theworking time compared to the conventional case of repeating movement andcontact of a probe by the number of short contact points.

In the case of the above embodiment, by first using one calibrationboard 50A, the phase of a clock signal is adjusted on the basis of eachstrobe signal. However, it is also allowed to adjust the phase of astrobe signal on the basis of the phase of each clock signal. Moreover,though the phase of a clock signal is adjusted (step 106 in FIG. 4)after adjusting the phase of a strobe signal by using the othercalibration board 50B (step 105 in FIG. 4), it is also allowed toreverse the above sequence.

[Second Embodiment]

In the case of the above-described embodiment, calibration is performedby using two types of calibration boards 50A and 50B in order. However,it is also allowed to save labor by using one type of a calibrationboard having functions of these two types of calibration boards 50A and50B.

FIGS. 12 and 13 are illustrations showing a configuration of acalibration board 50C of a second embodiment having functions of twotypes of calibration boards 50A and SOB, in which the calibration board50C is connected to a semiconductor test instrument 10 through aperformance board 30. The calibration board 50C shown in FIGS. 12 and 13is provided with two changeover switches correspondingly to each shortconnection point.

Specifically, a changeover switch 1 e is set nearby a short connectionpoint 1 c correspondingly to the short connection point 1 c and achangeover switch 1 d is set nearby a terminal 1 b corresponding to acomparator CP1. By changing over the changeover switch 1 d, it ispossible to selectively connect the terminal 1 b to either of the shortconnection points 1 c and 2 c. Moreover, by changing over the changeoverswitch 1 e, it is possible to selectively realize a state of connectingthe short connection point 1 c to terminals 1 a and 1 b in common and astate of connecting the short connection point 1 c to terminals 1 a andnb in common. The same is applied to another switch 2 d and the like.Wiring lengths between short connection points 1 c to nc and terminals 1a and 1 b and the like are set so that delay times of all signals areequalized.

As shown in FIGS. 12 and 13, by changing over the changeover switch 1 dand the like, it is possible to selectively realize wiring contents oftwo types of calibration boards 50A and 50B. Therefore, by using thecalibration board 50C and thereby changing over the changeover switchesto perform calibration, exchange of, calibration boards is unnecessaryand it is possible to further simplify working contents, reduce thecost, and shorten the working time.

[Third Embodiment]

In the case of the above embodiments, calibration is performed bycombining one driver with one comparator. However, it is also allowed toperform calibration every group formed by combining a plurality ofdrivers with a plurality of comparators.

FIG. 14 is an illustration showing a wiring state of one calibrationboard 150A used to perform calibration in this embodiment. Device socketends 1 g to 1 mg serving as m short connection points shown in FIG. 14correspond to the short connection points 1 c to nc of the calibrationboard 50A shown in FIG. 2. In FIG. 14, these connection points are drawnin a calibration board 150A according to convenience. However, in thecase of the calibration board 50A shown in FIG. 2 and the calibrationboard 150A shown in FIG. 14, it is not always necessary that each shortconnection point is exposed to the outside when noticing onlycalibration. Therefore, as illustrated in FIG. 14, it is allowed thateach short connection point 1 g or the like is embedded in a calibrationboard.

In FIG. 14, n terminals 1 a to na connected with n drivers DR1 to DRnform m number of groups by collecting every a predetermined number ofterminals (for examples, such as three terminals). The first group(group 1) includes terminals 1 a to 3 a corresponding to the drivers DR1to DR3 respectively and these terminals 1 a to 3 a are connected to oneshort connection point 1 g in common. The second group (group 2)includes terminals 4 a to 6 a corresponding to the drivers DR4 to DR6respectively and these terminals 4 a to 6 a are connected to one shortconnection point 2 g in common. The same is applied to terminals otherthan the terminals 1 a to 6 a. The m-th group (group m) includesterminals (n−2)a to na corresponding to drivers DRn−2 to DRn and theseterminals are connected to one short connection point mg in common.

Moreover, n terminals 1 b to nb connected with n comparators CP1 to CPnform m number of groups by collecting every a predetermined number ofterminals. The first group includes the terminals 1 b to 3 bcorresponding to the comparators CP1 to CP3 respectively and theterminals 1 b to 3 b are connected to one short connection point 1 g incommon. The second group includes the terminals 4 b to 6 b correspondingto the comparators CP4 to CP6 respectively and the terminals 4 b to 6 bare connected to one short connection point 2 g in common. The same isapplied to terminals other than the above terminals. The m-th group(group m) includes the terminals (n−2) b to nb corresponding to thecomparators CPn−2 to CPn respectively and these terminals are connectedto one short connection point mg in common.

Thus, the total of six terminals corresponding to three drivers andthree comparators respectively are connected to the short connectionpoints 1 g to mg respectively. Wirings for connecting terminals withshort connection points are set so that their lengths (time length) interms of signal delay time are all equalized.

FIG. 15 is an illustration showing a wiring state of the othercalibration board 150B used for calibration in this embodiment.

The calibration board 150B shown in FIG. 15 is different from thecalibration board 150A shown in FIG. 14 only in the correspondingrelation between the short connection points 1 g to mg and the terminals1 a to na connected to drivers. Specifically, the terminals 1 a to 3 acorresponding to the drivers DR1 to DR3 included in the first group areconnected to the short connection point mg included in the m-th group incommon. Moreover, the terminals 4 a to 6 a corresponding to the driversDR4 to DR6 included in the second group are connected to the shortconnection point 1 g in common. Thus, terminals corresponding to driversand short connection points are set so that the corresponding relationbetween the terminals and the points is shifted one group by one group.Also in the case of the calibration board 150B, wirings for connectingterminals with short connection points are set so that their wiringlengths (time lengths) in terms of signal delay time are equalized. Thatis, lengths of wirings for connecting terminals with short connectionpoints included in the two calibration boards 150A and 150B are set sothat they are all equalized.

The calibration boards 150A and 150B of this embodiment have the aboveconfigurations. Then, calibrations using these calibration boards 150Aand 150B are described below. It is assumed that the semiconductor testinstrument 10, performance board 30, and workstation 40 described forthe first embodiment are used for calibration boards other than thecalibration boards 150A and 150B.

FIG. 16 is an illustration showing initial states of a clock signal anda strobe signal in the semiconductor test instrument 10 beforeperforming calibration. FIG. 16 notices the timing at which a signaloutput from each driver reaches each comparator the same as the case ofFIG. 6 used for the first embodiment. As shown in FIG. 16, in an initialstate, the timing at which a signal output from each driver and input toeach comparator correspondingly to each of the clock signals CLK1 toCLKn does not coincide with the timing at which each of the strobesignals STB1 to STBn is input to each comparator.

FIG. 17 is a flowchart showing a calibration procedure of thisembodiment. After one calibration board 150A is set to the performanceboard 30 (step 200), the tester control section 12 adjusts the phase ofeach strobe signal on the basis of an optional clock signal every groupof the calibration board 150A (step 201).

As described above, this specification notices operations of acomparator when a signal generated by a driver correspondingly to aclock signal is input to the comparator in order to consider adjustmentof the phase of a clock signal or strobe signal. Therefore, adjustingthe phase of each strobe signal on the basis of an optional clock signalin step 201 just denotes adjusting the timing at which comparison isperformed by a comparator to the timing at which a signal output fromany driver in each group after inputting a clock signal to the driverand input to each comparator in the same group rises.

FIG. 18 is an illustration showing drivers and comparators to or fromwhich signals are input or output correspondingly to step 201. In FIG.18, drivers or comparators whose operations are valid are hatched. Asshown in FIG. 18, operations of the driver DR1 to which the clock signalCLK1 is input becomes valid in the group 1 and operations of threecomparators CP1 to CP3 to which a signal output from the driver DR1 isinput via the short connection pint 1 g become valid. Because the sameis applied to other groups, detailed description is omitted.

FIG. 19 is an illustration showing the outline of the strobe signalphase adjustment to be executed in step 201. First, the tester controlsection 12 notices the group 1, fixes the phase of the clock signal CLK1input to the driver DR1, that is, fixes timings at which signals inputto three comparators CP1 to CP3 via the short connection point 1 g rise,thereby varies phases of the strobe signals STB1 to STB3, searchespositions at which levels of outputs of the comparators CP1 to CP3 areinverted, and thus adjusts phases of the strobe signals STB1 to STB3 onthe basis of the clock signal CLK1. Then, the tester control section 12notices the group 2, fixes the phase of the clock signal CLK4 input tothe driver DR4, that is, fixes timings at which signals input to threecomparators CP4 to CP6 via the short connection point 2 g rise, therebyvaries phases of the strobe signals STB4 to STB6, searches positions atwhich levels of outputs of the comparators CP4 to CP6, and thus adjustsphases of the strobe signals STB4 to STB6 on the basis of the clocksignal CLK4. Thus, the tester control section 12 notices each group,fixes the phase of a clock signal input to any driver, thereby variesthe phase of strobe signal, searches positions at which levels ofoutputs of three comparators are inverted, and thus adjusts the phase ofeach strobe signal on the basis of a clock signal.

Thus, phases of strobe signals are adjusted every group. However, phasesof clock signals corresponding to groups used for the above phaseadjustment (timings at which signals corresponding to clock signals riseat input ends of comparators) do not coincide with each other.Therefore, at this stage, phases of strobe signals included in differentgroups do not coincide with each other. Moreover, it is not alwaysnecessary to start strobe signal phase adjustment with the group 1 butit is allowed to conform to an optional sequence or perform phaseadjustments in parallel.

Then, the tester control section 12 adjusts phases of clock signals onthe basis of any strobe signal every group of the calibration board 150A(step 202). In this case, adjusting phases of clock signals on the basisof any strobe signal just denotes adjusting phases of clock signals sothat the rise timing of a signal output from each driver coincides withthe timing of the comparison performed by any comparator while fixingthe phase of a strobe signal input to the comparator.

FIG. 20 is an illustration showing drivers and comparators to or fromwhich signals are input or output correspondingly to step 202. As shownin FIG. 20, for example, operations of three drivers DR1 to DR3 becomevalid in the group 1 and operations of the comparator CP1 to whichoutput signals of the drivers DR1 to DR3 are selectively input via theshort connection point 1 g become valid. Because the same is applied toother groups, detailed description is omitted.

FIG. 21 is an illustration showing the outline of the clock signal phaseadjustment to be executed in step 202. First, the tester control section12 notices the group 1, fixes the phase of the strobe signal STB1 inputto the comparator CP1, that is, fixes the timing of the comparisonperformed by the comparator CP1 and thereby adjusts the phase of theclock signal CLK2 so that the timing at which a signal output from thedriver DR2 and input to the comparator CP1 rises coincides with thecomparison timing of the comparator CP1. When the phase adjustmentcorresponding to the driver DR2 is completed, the phase of the clocksignal CLK3 is adjusted also for the driver DR3. Then, the testercontrol section 12 notices the group 2, fixes the phase of the strobesignal STB4 input to the comparator CP4, that is, fixes the timing ofthe comparison performed by the comparator CP4, and thereby adjusts thephase of the clock signal CLK5 so that the timing at which a signaloutput from the driver DR5 and input to the comparator CP4 risescoincides with the comparison timing of the comparator CP4. When thephase adjustment corresponding to the driver DR5 is completed, the phaseof the clock signal CLK6 is adjusted also for the driver DR6. Thus, thetester control section 12 notices each group, fixes the phase of astrobe signal input to any comparator, thereby varies the phase of aclock signal input to each driver, makes timings at which outputs ofthree drivers rise coincide with timings at which comparisons areperformed by comparators, and thus adjusts the phase of each clocksignal.

Thus, phases of clock signals are adjusted every group. However, phasesof strobe signals in each group used for the above phase adjustment donot coincide with each other. Therefore, at this stage, phases of clocksignals included in different groups do not coincide with each other.Moreover, it is not always necessary to start strobe signal phaseadjustment with the group 1 but it is allowed to perform the adjustmentin any sequence or in parallel for groups.

Thus, when operations for adjusting phases of clock signals and strobesignals corresponding to all drivers and comparators included in eachgroup are completed by using one calibration board 150A, the othercalibration board 150B is set (step 203). The calibration boards 150Aand 150B may be set in steps 200 and 203 manually or by an exclusiverobot in order to automate operations.

Then, the tester control section 12 obtains the phase difference of eachstrobe signal corresponding to a comparator included in a group on thebasis of a clock signal corresponding to any driver (step 204). Thereby,phase differences of strobe signals between groups are obtained.

FIG. 22 is an illustration showing drivers and comparators to or fromwhich signals are input or output correspondingly to step 204. As shownin FIG. 22, for example, operations of the comparators CP1 to CP3 becomevalid in the group 1 and operations of the driver DR4 included in thegroup 2 become valid in order to measure phase differences of the strobesignals STB1 to STB3 corresponding to these three comparators CP1 toCP3. Because the same is applied to other groups, detailed descriptionis omitted.

FIG. 23 is an illustration showing the outline of the strobe signalphase difference measurement to be executed in step 204. First, thetester control section 12 measures the phase difference T1 of each ofthe strobe signals STB1 to STB3 corresponding to the comparators CP1 toCP3 on the basis of the clock signal CLK4 corresponding to the driverDR4 included in the group 2. Specifically, the tester control section 12fixes phases of the strobe signals STB1 to STB3 input to the comparatorsCP1 to CP3, that is, fixes comparison timings of three comparators CP1to CP3 thereby varies the phase of the clock signal CLK4 correspondingto the driver DR4, searches positions at which outputs of thecomparators CP1 to CP3 are inverted, and thus measures the change valueof the phase of the clock signal CLK4 as the phase difference T1. Then,the tester control section 12 measures phase differences of the strobesignals STB4 to STB6 corresponding to the comparators CP4 to CP6included in the group 2 on the basis of the clock signal CLK7corresponding to the driver DR7 included in the group 3. Thus, thetester control section 12 measures the phase difference of a strobesignal corresponding to a comparator included in each group on the basisof a clock signal corresponding to a driver included in a differentgroup. Thereby, it is possible to obtain the phase shift of a strobesignal between groups.

In the above description, the phase of a clock signal is varied.However, it is also allowed to vary the phase of a strobe signal whilefixing the phase of a clock signal. Moreover, though phases of strobesignals corresponding to comparators included in each group mustcoincide with each other through the above phase adjustment in step 201,a fluctuation may occur at the time of actual measurement. Therefore, itis preferable to obtain an averaged phase difference every group byaveraging values of phase differences measured for three strobe signals.Or, it is also allowed to obtain and average phase differences of strobesignals on the basis of a clock signal corresponding to another driverin the same group. For example, to measure the phase difference T1 shownin FIG. 23, it is allowed to use the clock signals CLK5 and CLK6. Thus,by averaging measurement results, it is possible to reduce the number ofcalibration errors caused by the fluctuation of measurement results andimprove the measurement accuracy by uniforming measurement results inthe measurement performed after calibration.

Then, correction values of strobe signals are decided by using obtainedphase differences of the strobe signals between groups (step 205).Specifically, because relative phase differences of strobe signalsbetween two adjacent groups in step 204 are known by obtaining phasedifferences of strobe signals between groups, it is possible to decide acorrection value necessary to adjust, on the basis of the phase of astrobe signal corresponding to one group, the phase of a strobe signalcorresponding to the other group to the phase of a strobe signal servingas a criterion.

Thereafter, the tester control section 12 corrects the phase of a strobesignal corresponding to each group by using the decided correction value(step 206).

FIG. 24 is an illustration showing the outline of the strobe signalphase correction to be executed in step 206. For example, the testercontrol section 12 corrects the phases of the strobe signals STB4 toSTB6 corresponding to the comparators CP4 to CP6 included in the group 2by the correction value T1 obtained in step 206 so as to they coincidewith the phases of the strobe signals STB1 to STB3 corresponding to thecomparators CP1 to CP3 included in the group 1. Thus, the tester controlsection 12 can make phases of all strobe signals coincide with eachother by correcting phases of strobe signals corresponding tocomparators in each group by using the correction value obtained in step206.

Then, the tester control section 12 corrects phases of the clock signalsCLK1 to CLKn input to the drivers DR1 to DRn (step 207). This correctionis performed on the basis of the phase of a strobe signal correspondingto any comparator in each group.

FIG. 25 is an illustration showing drivers and comparators to or fromwhich signals are input or output correspondingly to step 207. As shownin FIG. 25, for example, operations of three drivers DR1 to DR3 becomevalid in the group 1 and operations of comparator CPn−2 included ingroup m become valid in order to correct phases of the clock signalsCLK1 to CLK3 corresponding to three drivers DR1 to DR3. Because the sameis applied to other groups, detailed description is omitted.

FIG. 26 is an illustration showing the outline of the clock signalcorrection to be executed in step 207. For example, the tester controlsection 12 corrects phases of the clock signals CLK4 to CLK6corresponding to three drivers DR4 to DR6 included in the group 2 on thebasis of a strobe signal corresponding to the comparator CP1 in thegroup 1. Thus, the tester control section 12 corrects phases of clocksignals corresponding to three drivers included in each group on thebasis of strobe signals corresponding to comparators included indifferent groups. Thereby, phases of all clock signals and strobesignals coincide with each other.

As described above, in the case of the semiconductor test instrument ofthis embodiment using the calibration boards 150A and 150B, clocksignals and strobe signals are first adjusted every group by using onecalibration board 150A. Then, by using the other calibration board 150B,phase differences of strobe signals are measured between groups andphases are corrected so as to eliminate phase differences of strobesignals and clock signals between groups in accordance with the measuredphase differences. Therefore, in the case of the calibration by thesemiconductor test instrument of this embodiment, it is unnecessary tocontact a probe every device socket end and only the calibration boards150A and 150B are set. It makes possible to simplify working contentsnecessary for calibration. Moreover, it is unnecessary to separately usea special configuration including a reference driver/comparator sectionand an exclusive robot for repeating contact and movement of a probe andthus, it is possible to greatly reduce the cost. Furthermore, becausethe operation followed by mechanical movement before calibration iscompleted includes only setting of the calibration boards 150A and 150B,it is possible to greatly shorten the working time compared to theconventional case of repeating movement and contact of a probe by thenumber of device socket ends. Furthermore, by dividing drivers andcomparators into a plurality of groups and using the phase differencedata measured every group, it is possible to reduce the number ofcalibration errors caused by the fluctuation of measurement results andimprove the measurement accuracy by uniforming measurement errorsthrough actual measurement performed after calibration.

In the case of the above embodiment, the phase of each strobe signal isfirst adjusted on the basis of an optional clock signal and then, thephase of each clock signal is adjusted in steps 201 and 202 shown inFIG. 17. However, it is also allowed to first adjust the phase of eachclock signal on the basis of an optional strobe signal and then adjustthe phase of each strobe signal.

Moreover, in step 204 shown in FIG. 17, the phase difference of eachstrobe signal is obtained on the basis of an optional clock signal.However, it is also allowed to obtain the phase difference of each clocksignal on the basis of an optional strobe signal.

Moreover, though the phase of a clock signal is adjusted (step 207 inFIG. 17) after adjusting the phase of a strobe signal by using thecalibration board 150B (step 206 in FIG. 17), it is also allowed toreverse the above sequence.

[Fourth Embodiment]

In the case of the above third embodiment, calibration is performed byusing two types of the calibration boards 150A and 150B in order.However, it is also allowed to use one type of a calibration boardhaving functions of the two calibration boards 150A and 150B so as tosave labor.

FIGS. 27 and 28 are illustrations showing a configuration of acalibration board 150C of a fourth embodiment having functions of twotypes of the calibration boards 150A and 150B different from each otherin wiring contents. The calibration board 150C shown in FIGS. 27 and 28is provided with two changeover switches every group.

Specifically, a changeover switch 1 j is set nearby a terminal 1 fconnected to output terminals of three drivers DR1 to DR3 correspondingto the group 1 in common and a changeover switch 1 k is set nearby aterminal 1 h connected to input terminals of three comparators CP1 toCP3 in common. Moreover, two changeover switches 2 j and 2 k are set tothe group 2 . . . and changeover switches mj and mk are set to the groupm.

By changing over the changeover switch 1 j, it is possible toselectively connect output ends of three drivers DR1 to DR3corresponding to the group 1 to either input ends of three comparatorsCP1 to CP3 corresponding to the group 1 or input ends of threecomparators CPn−2 to CPn corresponding to the group m. The same isapplied to other changeover switches and it is possible to selectivelyrealize two connection states Lengths of wirings for connecting outputends of the drivers with input end of the comparators are set so thatsignal delay times are all equalized independently of states ofchangeover switches.

As shown in FIGS. 27 and 28, by changing over the changeover switches 1j and 1 k, it is possible to selectively realize wiring contents of twotypes of the calibration boards 150A and 150B. Therefore, by using thecalibration board 150C and thereby changing over changeover switches andperforming calibration, exchange of calibration boards is unnecessaryand it is possible to further simplify working contents, reduce thecost, and shorten the working time.

[Fifth Embodiment]

Then, a method for calibrating a semiconductor test instrument of afifth embodiment using having wiring contents different from those ofthe above described embodiments is described below.

FIG. 29 is an illustration showing a wiring state of one calibrationboard 250A. A short connection point (device socket end) e shown in FIG.29 is drawn in the calibration board 250A according to illustration'sconvenience.

In FIG. 29, n terminals 1 a to na connected with n drivers DR1 to DRnform m number of groups by collecting every a predetermined number ofterminals (e.g. every three terminals). The first group (group 1)includes the terminals 1 a to 3 a corresponding to the drivers DR1 toDR3 respectively and among the terminals 1 a to 3 a, only the terminal 1a is connected to a short connection point e in common. The second group(group 2) includes the terminals 4 a to 6 a corresponding to the driversDR4 to DR6 respectively and among the terminals 4 a to 6 a, only theterminal 4 a is connected to the short connection point e in common. Thesame is applied to other terminals and the m-th group (group m) includesthe terminals (n−2) a to na corresponding to the drivers DRn−2 to DRnrespectively and among the terminals (n−2) a to na, only the terminal(n−2) a is connected to the short connection point e in common.

Moreover, n terminals 1 b to nb connected with n comparators CP1 to CPnform m number of groups by collecting every a predetermined number ofterminals. The first group includes the terminals 1 b to 3 bcorresponding to the comparators CP1 to CP3 respectively and among theterminals 1 b to 3 b, only the terminal 1 b is connected to the shortconnection point e. The second group includes the terminals 4 b to 6 bcorresponding to the comparators CP4 to CP6 respectively. The same isapplied to other terminals and the m-th group (group m) includes theterminals (n−2) b to nb corresponding to the comparators CPn−2 to CPnrespectively.

Thus, the unique short connection point e set to the calibration board250A is connected to a terminal corresponding to one driver (this isreferred to as in-group common driver) of three drivers included in eachgroup in common and moreover connected to a terminal corresponding toone comparator (this is referred to as common comparator) of threecomparators included in the group 1. Wirings for connecting terminalswith the short connection point e are set so that their wiring lengths(time lengths) in terms of signal delay time are set so as to be allequalized.

FIG. 30 is an illustration showing a wiring state of the othercalibration board 250B. The m short connection points 1 g to mg shown inFIG. 30 are drawn in the calibration board 250B for reasons ofillustration. However, because it is not always necessary that eachshort connection point is exposed to the outside, it is allowed that theshort connection point 1 g and the like are embedded in the calibrationboard as illustrated in FIG. 30. The other calibration board 250B shownin FIG. 30 has the same wiring state as the calibration board 150A shownin FIG. 14 and description of a wiring state is omitted.

The calibration boards 250A and 250B of this embodiment have the aboveconfigurations. Then, calibrations using these calibration boards aredescribed below. In this case, it is assumed that clock signals andstrobe signals in the semiconductor test instrument 10 beforecalibration are respectively kept in the initial state shown in FIG. 16.

FIG. 31 is a flowchart showing a calibration procedure of thisembodiment. After one calibration board 250A is set to a performanceboard 30 (step 300), a tester control section 12 adjusts phases of clocksignals CLK1, CLK4, . . . , and CLKn−2 corresponding to drivers(in-group common drivers) DR, DR4, . . . , and DRn−2 included in eachgroup on the basis of a strobe signal STBL corresponding to a comparatorCP1 of the calibration board 250A (step 301).

In the above step 301, it is necessary to adjust the phase of the clocksignal CLK1 or the like on the basis of the strobe signal STB1.Therefore, the phase of the clock signal CLK1 or the like is adjusted byobserving the level of an output signal of the comparator CP1 when thestrobe signal STB1 is output (raised) and comparison is performed by thecomparator CP1 while changing the rise timing of the clock signal CLK1or the like little by little and obtaining the phase of the clock signalCLK1 or the like when the level of an output signal of the comparatorCP1 is just inverted. The above operation is performed for the clocksignals CLK1, CLK4, . . . , and CLKn−2 in order.

FIG. 32 is an illustration showing drivers and comparators to or fromwhich signals are input or output correspondingly to step 301. In FIG.32, a driver or comparator whose operations are valid is hatched. Asshown in FIG. 32, operations of the driver DR1 to which the clock signalCLK1 is input become valid and operations of the comparator CP1 to whicha signal output from the driver DR1 is input via the short connectionpoint e become valid in the group 1. Moreover, in another group,operation of a driver to which a clock signal is input becomes valid.For example, operations of the driver DR4 become valid in the group 2and operations of the driver DRn−2 become valid in the group m.

FIG. 33 is an illustration showing the outline of the clock signal phaseadjustment to be executed in step 301. First, the tester control section12 notices the driver DR1 in the group 1, fixes the phase of the strobesignal STB1 input to the comparator CP1, that is, fixes the timing forperforming comparison by the comparator CP1, thereby varies the phase ofthe clock signal CLK1, searches a position at which the level of anoutput of the comparator CP1 is inverted, and thus adjusts the phase ofthe clock signal CLK1. Then, the tester control section 12 notices thedriver DR4 in the group 2, fixes the phase of the strobe signal STB1input to the comparator CP1, thereby varies the phase of the clocksignal CLK4, and searches a position at which the level of an output ofthe comparator CP1 is inverted, and thus adjusts the phase of the clocksignal CLK4. Thus, the tester control section 12 notices one driverincluded in each group, fixes the phase of the strobe signal STB1 inputto the comparator CP1, thereby varies the phase of a clock signal inputto each driver, searches a position at which the level of an output ofthe comparator CP1 is inverted, and thus adjusts the phase of each clocksignal.

Thus, the phase of a clock signal is adjusted on the basis of the commonstrobe signal STB1 every group. It is not always necessary to start thephase adjustment of a clock signal with the group 1 but it is allowed tostart the phase adjustment with any group.

Thus, when adjustment of a clock signal input to an in-group commondriver included in each group on the basis of the strobe signal STB1input to the common comparator CP1 by using one calibration board 250Ais completed, the other calibration board 250B is set (step 302). Thecalibration boards 250A and 250B may be set in steps 300 and 302manually or by using an exclusive robot in order to automate working.

Then, the tester control section 12 adjusts the phase of each strobesignal on the basis of a clock signal whose phase adjustment iscompleted every group of the calibration board 250B (step 303).

FIG. 34 is an illustration showing drivers and comparators to or fromwhich signals are input or output correspondingly to step 303. As shownin FIG. 34, operations of the driver DR1 to which the clock signal CLK1is input become valid and operations of two comparators CP2 and CP3 towhich signals output from the driver DR1 are input via the shortconnection point 1 g become valid in the group 1. Moreover, in the group2, operations of the driver DR4 to which the clock signal CLK4 is inputbecome valid and operations of three comparators CP4 to CP6 to whichsignals output from the driver DR4 are input via a short connectionpoint 2 g. Because cases of other groups are basically the same as thecase of the group 2, detailed description is omitted.

FIG. 35 is an illustration showing the outline of the strobe signalphase adjustment to be executed in step 303. First, the tester controlsection 12 notices the group 1, fixes the phase of the clock signal CLK1input to the driver DR1, that is, fixes rise timings of signals input totwo comparators CP2 and CP3 via the short connection point 1 g, therebyvaries phases of the strobe signals STB2 and STB3, searches positions atwhich levels of outputs of the comparators CP2 and CP3 are inverted, andthus adjusts phases of the strobe signals STB2 and STB3 on the basis ofthe clock signal CLK1. Then, the tester control section 12 notices thegroup 2, fixes the phase of the clock signal CLK4 input to the driverDR4, that is, fixes rise timings of signals input to three comparatorsCP4 to CP6 via the short connection point 2 g, thereby varies phases ofthe strobe signals STB4 to STB6, searches positions at which levels ofoutputs of the comparators CP4 to CP6 are inverted, and thus adjustsphases of the strobe signals STB4 to STB6 on the basis of the clocksignal CLK4. For groups 3 to m, the tester control section 12 fixes thephase of one clock signal whose phase adjustment is completed for eachgroup, thereby varies the phase of a strobe signal, searches positionsat which levels of outputs of three comparators, and thus adjusts thephase of each strobe signal on the basis of one clock signal.

Thus, phases of strobe signals are adjusted every group. It is notalways necessary to start phase adjustment of strobe signals with thegroup 1. It is allowed to start the phase adjustment with any group orin parallel for groups.

Then, the tester control section 12 adjusts the phase of each clocksignal on the basis of any strobe signal every group (step 304).

FIG. 36 is an illustration showing drivers and comparators to or fromwhich signals are input or output correspondingly to step 304. As shownin FIG. 36, for example, in the group 1, operations of the drivers DR2and DR3 to which two clock signals CLK2 and CLK3 whose phase adjustmentis not completed are input become valid and operations of the comparatorCP1 to which signals output from the drivers DR2 and DR3 are input viathe short connection point 1 g become valid. Because the same is appliedto other groups, detailed description is omitted.

FIG. 37 is an illustration showing the outline of the clock signal phaseadjustment to be executed in step 304. First, the tester control section12 notices the group 1, fixes the phase of the strobe signal STB1 inputto the comparator CP1, that is, fixes the timing of the comparisonperformed by the comparator CP1, and thereby adjusts the phase of theclock signal CLK2 so that the rise timing of a signal output from thedriver DR2 coincides with the comparison timing of the comparator CP1.When the phase adjustment corresponding to the driver DR2 is completed,the phase of the clock signal CLK3 is also performed for the driver DR3.Then, the tester control section 12 notices the group 2, fixes the phaseof the strobe signal STB4 input to the comparator CP4, that is, fixesthe timing of the comparison performed by the comparator CP4, andthereby adjusts the phase of the clock signal CLK5 so that the risetiming of a signal output from the driver DR5 coincides with thecomparison timing of the comparator CP4. When the phase adjustmentcorresponding to the driver DR5 is completed, the phase of the clocksignal CLK6 is also adjusted for the driver DR6. Thus, the testercontrol section 12 notices each group, fixes the phase of a strobesignal input to any comparator, varies the phase of a clock signal inputto each driver, makes rise timings of outputs of two drivers whose phaseadjustment is not completed coincide with the timing at which comparisonis performed by the comparator, and thereby adjusts the phase of eachclock signal.

In the above description, the comparator CP1 is used as a commoncomparator in the group 1. However, it is allowed to use any one ofother comparators CP2 and CP3 as a common comparator. The same isapplied to other groups.

Thus, a series of calibrations for adjusting phases of all clock signalsand strobe signals is completed.

As described above, in the case of the semiconductor test instrument ofthis embodiment, the phase of a clock signal input to an in-group commondriver in each group is first adjusted on the basis of the strobe signalSTB1 input to the common comparator CP1 by using one calibration board250A. Then, by using the other calibration board 250B, the phase of eachstrobe signal is adjusted on the basis of the clock signal whose phaseadjustment is completed every group and thereafter, phases of remainingclock signals whose phase adjustments is not completed are adjusted onthe basis of any strobe signal whose phase adjustment is completed.Therefore, in the case of the calibration of the semiconductor testinstrument of this embodiment, it is not necessary to contact a probeevery device socket end but it is only necessary to set the calibrationboards 250A and 250B. Therefore, the working contents necessary forcalibration are simplified. Moreover, a special configuration such as aseparate reference driver/comparator section or an exclusive robot forrepeating contact and movement of a probe is unnecessary for calibrationand thus, it is possible to greatly reduce the cost. Moreover, becauseonly setting of the calibration boards 250A and 250B is the workingfollowed by mechanical movement before calibration is completed, it ispossible to greatly shorten the working time compared to theconventional case of repeating movement and contact of a probe by thenumber of device socket ends.

[Sixth Embodiment]

The above fifth embodiment uses the calibration board 250A in which mdrivers DR1, DR4, . . . , and DRn−2 included in each group and onecomparator CP1 are connected to the short connection point e. Instead,however, it is also allowed to use a calibration board 250C in which onedriver (common driver) DR1 and m comparators (in-group commoncomparators) cP1, CP4 . . . , and CPn−2 included in each group areconnected to the short connection point e as shown in FIG. 38.

FIG. 39 is a flowchart showing a calibration procedure of thisembodiment performed by combining the calibration board 250C shown inFIG. 38 with the calibration board 250B shown in FIG. 30. After onecalibration board 250C is set to a performance board 30 (step 400), thetester control section 12 adjusts phases of the strobe signals STB1,STB4, . . . , and STBn−2 corresponding to the comparators CP1, CP4, . .. , and CPn−2 included in each group on the basis of the phase of theclock signal CLK1 corresponding to the driver DR1 of the calibrationboard 250C (step 401).

As described above, when adjustments of phases of strobe signals inputto one in-group common comparator included in each group on the basis ofthe clock signal CLK1 input to the common driver DR1 every group byusing one calibration board 250C are completed, the other calibrationboard 250B is set (step 402).

Then, the tester control section 12 adjusts the phase of each clocksignal on the basis of a strobe signal whose phase adjustment iscompleted every group of the calibration board 250B (step 403).Moreover, the tester control section 12 adjusts the phase of each strobesignal on the basis of any clock signal every group (step 404). Thus, aseries of calibrations for adjusting phases of all clock signals andstrobe signals is completed.

[Seventh Embodiment]

In the case of the above fifth and sixth embodiments, calibration isperformed by using two types of calibration boards in order. However, itis also allowed to use one type of a calibration board having functionsof these two types of calibration boards so as to save labor forexchange.

FIGS. 40 and 41 are illustrations showing a configuration of acalibration board 250D of a seventh embodiment having functions of twotypes of calibration boards 250A and 250B different from each other inwiring contents. The calibration board 250D shown in FIGS. 40 and 41 hastwo changeover switches correspondingly to the group 1 and onechangeover switch correspondingly to each group other than the group 1.

Specifically, a changeover switch 1 j connected to each of output endsof three drivers DR1 to DR3 and a changeover switch 1 k connected toeach of input ends of three comparators CP1 to CP3 are set so as tocorrespond to the group 1. Moreover, a changeover switch 2 j connectedto each of output ends of three drivers DR4 to DR6 is set so as tocorrespond to the group 2. Furthermore, changeover switches are set toeach of output ends of three drivers so as to correspond to each ofother groups. By changing over connection states of the changeoverswitches 1 j to mj and 1 k, it is possible to selectively realize theconnection state (FIG. 40) same as the case of one calibration board250A shown in FIG. 29 and the connection state (FIG. 41) same as thecase of the other calibration board 250B shown in FIG. 30. Therefore, byusing the calibration board 250D and thereby changing over eachchangeover switch to perform calibration, exchange of calibration boardsis unnecessary and it is possible to further simplify the workingcontents, reduce the cost, and shorten the working time.

FIGS. 42 and 43 are illustrations showing a configuration of acalibration board 250E of a modification of this embodiment havingfunctions of two types of calibration boards 250C and 250B differentfrom each other in wiring contents. The calibration board 250E shown inFIGS. 42 and 43 has two changeover switches correspondingly to the group1 and one changeover switch correspondingly to each group other than thegroup 1.

Specifically, a changeover switch. 1 j connected to each of output endsof three drivers DR1 to DR3 and a changeover switch 1 k connected toeach of input ends of three comparators CP1 to CP3 are set so as tocorrespond to the group 1. Moreover, a changeover switch 2 k connectedto each of input ends of three comparators CP4 to CP6 is set so as tocorrespond to the group 2. Similarly, changeover switches are set toeach of input ends of three comparators so as to correspond to each ofother groups. By changing over connection states of the changeoverswitches 1 j and 1 k to mk set to the calibration board 250E, it ispossible to selectively realize the connection state (FIG. 42) same asthe case of one calibration board 250C shown in FIG. 38 and theconnection state (FIG. 43) same as the case of the other calibrationboard 250B shown n FIG. 30. Therefore, by using the calibration board250E and thereby changing over changeover switches to performcalibration, exchange of calibration boards is unnecessary and it ispossible to further simplify the working contents, reduce the cost, andshorten the working time.

[Eighth Embodiment]

Then, a method for calibrating a semiconductor test instrument of aneighth embodiment using another calibration board is described below.

FIGS. 44 to 48 are illustrations showing wiring states of calibrationboards used for the calibration method of this embodiment. Lengths ofwirings for connecting short connection points 1 p and 1 q and the likewith terminals 1 a and 1 b and the like shown in FIGS. 44 to 48 are setso that they are set so as to be all equalized.

FIG. 44 is an illustration showing a wiring state of one calibrationboard 350A-1 of this embodiment. In the case of the calibration board350A-1, only a terminal 1 a among n terminals 1 a to na connected with ndrivers DR1 to DRn respectively is connected to the short connectionpoint 1 p. Moreover, only a terminal 1 b among n terminals 1 b to nbconnected with n comparators CP1 to CPn is connected to the above shortconnection point 1 p. That is, by using the calibration board 350A-1, asignal output from the driver DR1 is input to the comparator CP1 via theshort connection point 1 p.

FIG. 45 is an illustration showing a wiring state of another calibrationboard 350A-2. In the case of the calibration board 350A-2, only aterminal 1 a among n terminals 1 a to na connected to n drivers DR1 toDRn respectively is connected to a short connection point 2 p. Moreover,only a terminal 2 b among n terminals 1 b to nb connected with ncomparators CP1 to CPn respectively is connected to the above shortconnection point 2 p. That is, by using the calibration board 350A-2, asignal output from the driver DR1 is input to the comparator CP2 via theshort connection point 2 p.

FIG. 46 is an illustration showing a wiring state of another calibrationboard 350A-3 of this embodiment. In the case of the calibration board350A-3, only a terminal 1 a among n terminals 1 a to na connected with ndrivers DR1 to DRn respectively is connected to a short connection point3 p. Moreover, only a terminal 3 b among n terminals 1 b to nb connectedwith n comparators CP1 to CPn respectively is connected to the aboveshort connection point 3 p. That is, by using the calibration board350A-3, a signal output from the driver DR1 is input to anothercomparator CP3 via the short connection point 3 p.

FIG. 47 is an illustration showing a wiring state of another calibrationboard 350A-n of this embodiment. In the case of the calibration board350A-n, only a terminal 1 a among n terminals 1 a to na connected with ndrivers DR1 to DRn respectively is connected to a short connection pointnp. Moreover, only a terminal nb among n terminals 1 b to nb connectedwith n comparators CP1 to CPn respectively is connected to the aboveshort connection point np. That is, by using the calibration board350A-n, a signal output from the driver DR1 is input to the comparatorCPn via the short connection point np.

This embodiment uses n calibration boards 350A-1 to 350A-n in order toconnect any one of n comparators CP1 to CPn with the driver DR1 througha short connection point.

Moreover, FIG. 48 is an illustration showing a wring state of anothercalibration board 350B of this embodiment. In the case of thecalibration board 350B, n terminals 1 a to na connected with n driversDR1 to DRn are connected to short connection points 1 q to nq inone-to-one correspondence. Moreover, these short connection points 1 qto nq are also connected to n comparators CP1 to CPn respectively.Thereby, signals output from the drivers DR1 to DRn are input to thecomparators CP1 to CPn via respectively corresponding separate shortconnection points 1 q to nq.

FIG. 49 is a flowchart showing a calibration procedure of thisembodiment. After one calibration board (e.g. calibration board 350A-1)is set to the performance board 30 (step 500), the tester controlsection 12 adjusts the phase of the strobe signal STB1 corresponding tothe comparator CP1 of the calibration board 350A-1 connected with thedriver DR1 through the short connection point 1 p on the basis of theclock signal CLK1 corresponding to the driver DR1 (step 501).

In this step 501, the phase of the strobe signal STB1 is adjusted byvarying the phase of the strobe signal STB1 and searching a position atwhich the level of an output of the comparator CP1 is inverted whilefixing the phase of the clock signal CLK1 input to the driver DR1, thatis, while fixing the rise timing of a signal input to the comparator CP1via the short connection point 1 p.

Then, the tester control section 12 determines whether any unadjustedstrobe signal is left (step 502). When any unadjusted strobe signal isleft, step 501 is restarted to repeat operations from the operation forsetting the next calibration board (e.g. calibration board 350A-2)downward. Thus, by using the calibration boards 350A-1 to 350A-n shownin FIGS. 44 to 47, phases of strobe signals STB1 to STBn input to ncomparators CP1 to CPn respectively are adjusted on the basis of theclock signal CLK1 input to the driver DR1.

Thus, when adjustments of phases of all strobe signals are completed(negative determination in step 502), another calibration board 350B isset (step 503). The calibration boards 350A-1 to 350A-n and 350B may beset in steps 500 and 503 manually or by using an exclusive robot inorder to automate the working.

Then, the tester control section 12 adjusts the phase of each clocksignal on the basis of each strobe signal whose phase adjustment iscompleted by using the calibration board 350B (step 504). As describedabove, in the case of the calibration board 350B, the driver DR1 isconnected to the comparator CP1 through the short connection point 1 q.Therefore, it is possible to adjust the phase of the clock signal CLK1on the basis of the strobe signal STBL. Moreover, because the driver DR2is connected to the comparator CP2 through the short connection point 2q, it is possible to adjust the phase of the clock signal CLK2 on thebasis of the strobe signal STB2. Furthermore, because the driver DRn isconnected to the comparator CPn through the short connection point nq,it is possible to adjust the phase of the clock signal CLKn on the basisof the strobe signal STBn.

Thus, a series of calibrations for adjusting phases of all strobesignals and clock signals is completed.

In the case of this embodiment, phases of n strobe signals STB1 to STBnare first adjusted on the basis of the clock signal CLK1 and then,phases of n clock signals CLK1 to CLKn are adjusted on the basis of eachstrobe signal. However, it is also allowed to first adjust phases of nclock signals CLK1 to CLKn on the basis of one strobe signal and thenadjust phases of n strobe signals STB1 to STBn on the basis of eachclock signal.

Moreover, in the case of this embodiment, n calibration boards 350A-1 to350A-n are set in order to adjust phases of n strobe signals STB1 toSTBn on the basis of the clock signal CLK1. However, as shown in FIG.50, it is also allowed to adjust phases of the strobe signals STB1 toSTBn by using a calibration board 350C in which n comparators CP1 to CPnare all connected to one short connection point.

Furthermore, though this embodiment uses the calibration board 250B inwhich each of the drivers DR1 to DRn corresponds one-to-one to each ofthe comparators CP1 to CPn, it is not always necessary that each of thedrivers DR1 to DRn correspond to each of the comparators CP1 to CPnone-to-one.

[Ninth Embodiment]

The eighth embodiment, calibration performed by using n+1 calibrationboards in order. However, it is also allowed to use one type of acalibration board having functions of these calibration boards so as tosave labor.

FIG. 51 is an illustration showing a configuration of a calibrationboard 350D of a ninth embodiment having functions of n+1 calibrationboards 350A-1 to 350A-n and 350B.

The calibration board 350D shown in FIG. 51 has changeover switches 2 rto nr corresponding to the comparators CP2 to CPn except the comparatorCP1. By changing over connection states of these changeover switches 2 rto nr, it is possible to selectively realize the connection state sameas the case of each of calibration boards 350A-1 to 350A-n and theconnection state same as the case of the calibration board 350B.Therefore, by using the calibration board 350D, the exchange ofcalibration boards is unnecessary and it is possible to further simplifythe working contents, reduce the cost, and shorten the working time.

FIG. 52 is an illustration showing a modification of the calibrationboard 350D shown in FIG. 51. When first adjusting the phase of eachclock signal on the basis of one strobe signal and then adjusting thephase of each strobe signal, it is allowed to change over connectionstates of switches 2 s to ns by using the calibration board 350E shownin FIG. 52.

[Other Embodiments]

For each of the above embodiments, various calibration boards are set tothe performance board 30. However, by considering an actual settingstate, it is also allowed to mount a socket board and IC socket on theperformance board 30 and moreover, set a calibration board on them.

FIG. 53 is an illustration showing a modification in which the settingstate of a calibration board is changed. In the case of theconfiguration shown in FIG. 53, a socket board (SB) 32 and an IC socket34 are added between the performance board (PB) 30 and the calibrationboard (CB) 50A on the configuration shown in FIG. 5. That is, thecalibration board 50A and the like are set while mounting the socket 32and IC socket 34 used to actually apply various tests to a DUT. In thiscase, though the wiring length between the output end of each driver andeach short connection point and the wiring length between eachconnection point and the input end of each comparator increase, it ispossible to perform calibration in accordance with the procedure same asthe case of each of the above embodiments.

For example, when rewriting FIG. 7 by assuming the length of the wiringincluded in the socket board 32 and IC socket 34 as Tb, relations shownin FIG. 54 are obtained. The output timing of a signal by each driverand the input timing of a signal to each comparator shown in FIG. 54 arethe same as the timings shown in FIG. 7. Therefore, it is found thattiming calibration can be performed in accordance with the proceduresame as the case of each embodiment while the socket board 32 and ICsocket 34 are set.

Moreover, in the case of each of the above embodiments, timingcalibration is performed by using various calibration boards. However,it is also allowed to use a calibration device or calibration wafer inthe same wiring state instead of the above calibration boards.

FIG. 55 is an illustration showing a connection state between acalibration device and a semiconductor test instrument. Moreover, FIG.56 is an illustration showing the outline of the timing calibrationusing a calibration device. As shown in FIG. 55, a calibration device450 is set while the performance board (PB) 30, socket board (SB) 32,and IC socket 34 are set to the semiconductor test instrument 10. Thecalibration device 450 has the same external shape and terminal shape asa DUT and the internal wiring state is set like the case of thecalibration board of each embodiment. In the case of each of the aboveembodiments, it is necessary to exchange calibration boards manually orautomatically by a robot according to necessity. However, when using thecalibration device 450, it is possible to exchange the calibrationdevice 450 by using a handler 100 for exchanging DUTs in the normalsemiconductor test. Therefore, it is possible to save the labor forexchange compared to the case of performing manual exchange. Moreover,it is possible to reduce the cost compared to the case of performingautomatic exchange by an exclusive robot because the robot isunnecessary.

FIG. 57 is an illustration showing a connection state between acalibration wafer and a semiconductor test instrument. FIG. 58 is anillustration showing the outline oft the timing calibration using acalibration wafer. To test a DUT that formed on a wafer by using thesemiconductor test instrument, a probe card (PC) 36 is set to theperformance board 30 to bring a needle 38 protruded from the probe card36 into contact with a pad formed on a wafer. Therefore, by replacingthe wafer in which the DUT is formed with a calibration wafer 550 whoseinternal wiring state is set the same as the wiring state of thecalibration board of each embodiment above described, it is possible toperform timing calibration. Moreover, in the case of each embodimentdescribed above, it is necessary to manually exchange calibration boardsor automatically exchange calibration boards by a robot. However, whenusing the calibration wafer 550, it is possible to exchange thecalibration wafer 550 by using a chuck 110 for moving a wafer to bemeasured in the normal semiconductor test. Therefore, it is possible tosave the labor for exchange compared to the case of performing manualexchange. Moreover, it is possible to reduce the cost compared to thecase of performing automatic exchange by an exclusive robot because therobot is unnecessary. In the case of examples shown in FIGS. 57 and 58,a semiconductor test instrument for securing an electrical contact withthe calibration wafer 550 or a wafer in which a DUT is actually formedby the needle 38 on the probe card 36 is described. However, it is alsoallowed to secure an electrical contact by a method other than theneedle 38 or through, for example, a bump.

Then, a specific example of the above calibration device 450 isdescribed below.

FIGS. 59 and 60 are illustrations showing calibration devices realizingthe same wiring state as the case of the calibration boards used for theabove first embodiment. One calibration device 450A shown in FIG. 59 hasthe same wiring state as the calibration board 50A shown in FIG. 2.Moreover, the other calibration board 450B shown in FIG. 60 has the samewiring state as the calibration board 50B shown in FIG. 3. Terminals andshort connection points of the calibration devices 450A and 450B shownin FIGS. 59 and 60 are provided with the same numeral numbers ascorresponding terminals and short connection points of the calibrationboards 50A and 50B shown in FIGS. 2 and 3. By setting these calibrationdevices 450A and 450B in order, it is possible to execute timingcalibration in accordance with the procedure (operation procedure shownin FIG. 4) same as the case of the first embodiment using thecalibration boards 50A and 50B.

FIGS. 61 and 62 are calibration devices realizing the same wiring stateas the case of the calibration boards used for the above thirdembodiment. One calibration device 450C shown in FIG. 61 has the samewiring state as the calibration board 150A shown in FIG. 14. Moreover,the other calibration device 450D has the same wiring state as thecalibration board 150B shown in FIG. 15. By setting these calibrationdevices 450C and 450D in order, it is possible to execute timingcalibration in accordance with the procedure (operation procedure shownin FIG. 17) same as the case of the third embodiment using thecalibration boards 150A and 150B.

FIG. 63 is an illustration showing a calibration device realizing thesame wiring state as the case of the calibration boards used for theabove fifth embodiment. The calibration device 450E shown in FIG. 63 hasthe same wiring state as the calibration board 250A shown in FIG. 29.Because the wiring state of the calibration board 250B shown in FIG. 30is the same as the wiring state of the calibration device 450C shown inFIG. 61, the calibration device 450C is used by being combined with theabove calibration device 450E. By setting these calibration devices 450Eand 450C in order, it is possible to execute timing calibration inaccordance with the procedure (operation procedure shown in FIG. 31)same as the case of the fifth embodiment using the calibration boards250A and 250B.

FIGS. 64 to 68 are illustrations showing calibration devices realizingthe same wiring state as the case of the calibration boards used for theabove eighth embodiment. The calibration devices 450F-1 shown in FIG. 64has the same wiring state as the calibration board 350A-1 shown in FIG.44. The calibration device 450F-2 shown in FIG. 65 has the same wiringstate as the calibration board 350A-2 shown in FIG. 45. The calibrationdevice 450F-3 shown in FIG. 66 has the same wiring state as thecalibration board 350A-3 shown in FIG. 46. The calibration device 450F-nhas the same wiring state as the calibration board 350A-n shown in FIG.47. Moreover, the calibration device 450G shown in FIG. 68 has the samewiring state as the calibration board 350B shown in FIG. 48. By settingthese calibration devices 450F-1 t 450F-n and 450G in order, it ispossible to execute timing calibration in accordance with the procedure(operation procedure shown in FIG. 49) same as the case of the eighthembodiment using the calibration boards 350A-1 to 350A-n and 350B.

Then, specific examples of the above calibration devices 450 aredescribed below.

FIG. 69 is an illustration showing a calibration wafer realizing thesame wiring state as the case of the calibration boards used for theabove first embodiment. Because the calibration wafer shown in FIG. 69or the like is used to realize the same wiring state as the case of theabove calibration boards, it is not always necessary to use a waferformed by a semiconductor material but it is allowed to form acalibration board by using an inexpensive material other than asemiconductor material such as epoxy resin.

The calibration wafer 550A shown in FIG. 69 includes a first region550A-1 in which the same wiring as the case of the calibration board 50Ashown in FIG. 2 is made and a second region 550A-2 in which the samewiring as the case of the calibration board 50B shown in FIG. 3 is made.By bringing the needle 38 of the probe card 36 into contact with thesefirst and second regions 550A-1 and 550A-2 in order, it is possible toexecute timing calibration in accordance with the procedure (operationprocedure shown in FIG. 4) same as the case of the first embodimentusing the calibration boards 50A and 50B.

FIG. 70 is an illustration showing a calibration wafer realizing thesame wiring state as the case of the calibration board used for theabove third embodiment. The calibration wafer 550B shown in FIG. 70includes a first region 550B-1 in which the same wiring as the case ofthe calibration board 150A shown in FIG. 14 is made and a second region550B-2 in which the same wiring as the case of the calibration board250B in FIG. 15 is made. By bringing the needle 38 of the probe card 36into contact with these first and second regions 550B-1 and 550B-2 inorder, it is possible to execute timing calibration in accordance withthe procedure (operation procedure shown in FIG. 17) same as the case ofthe third embodiment using the calibration boards 150A and 150B.

FIG. 71 is an illustration showing a calibration wafer realizing thesame wiring state as the case of the calibration boards used for theabove fifth embodiment. The calibration wafer 550C shown in FIG. 71includes a first region 550C-1 in which the same wiring as the case ofthe calibration board 250A shown in FIG. 29 is made and a second region550C-2 in which the same wiring as the case of the calibration board250B shown in FIG. 30 is made. By bringing the needle 38 of the probecard 36 into contact with these first and second regions 550C-1 and550C-2 in order, it is possible to execute timing calibration inaccordance with the procedure (operation procedure shown in FIG. 31)same as the case of the fifth embodiment using the calibration boards250A and 250B.

FIG. 72 is an illustration showing a calibration wafer realizing thesame wiring state as the case of the calibration boards used for theabove eighth embodiment. The calibration wafer 550D shown in FIG. 72includes a region 550D-1 in which the same wiring as the case of thecalibration board 350A-1 shown in FIG. 44 is made, a region 550D-2 inwhich the same wiring as the case of the calibration board 350A-2 shownin FIG. 45, a region 550D-3 in which the same wiring as the case of thecalibration board 350A-3 shown in FIG. 46, a region 550D-n in which thesame wiring as the case of the calibration board 350A-n shown in FIG.47, and a region 550D-B in which the same wiring as the case of thecalibration board 350B shown in FIG. 48. By bringing the needle 38 ofthe probe card 36 into contact with these regions 550D-1 to 550D-n and550D-B in order, it is possible to execute timing calibration inaccordance with the procedure (operation procedure shown in FIG. 49)same as the case of the eighth embodiment using the calibration boards350A-1 to 350A-n and 350B.

The present invention is not restricted to the above embodiments.Various modifications can be embodied in the range of the gist of thepresent invention. For example, though exclusive calibration boards 50A,50B, 150A, and 150B are used for the above embodiment, it is alsoallowed to change wiring contents by applying the same wiring as thecase of the calibration board 50B, 150A, or 150B to a socket board andproperly changing over changeover switches at the time of calibrationoperation.

Moreover, though a case in which the output end of a driver and theinput end of a comparator both of which constitute a set are separatelyconnected to a short connection point is considered for the aboveembodiments, it is also possible to apply the present invention to acase in which the output end of a driver and the input end of acomparator are connected each other in the semiconductor test instrument10 or performance board 30 and the connection point and the input endand a short connection point are connected each other through onewiring. However, because an object of phase correction through thecalibration in the above case is the range up to the above connectionpoint, it is necessary to previously measure the time length of thewiring between the connection point and the short connection point.

INDUSTRIAL APPLICABILITY

As described above, according to the present invention, it isunnecessary to use a reference driver/comparator section, a probeconnected to the section, and exclusive robot for automating movementand contact of the probe only to perform timing calibration. Therefore,it is possible to greatly reduce the cost.

Moreover, it is possible to adjust phases of a clock signal and a strobesignal and measure the phase difference between strobe signals by usinga first or second calibration board. Therefore, it is possible tosimplify working contents compared to the conventional method in whichthe phase of a clock signal or strobe signal is adjusted every devicesocket end by using a probe. Particularly, because mechanical workingincludes only exchange of a first calibration board to a secondcalibration board, it is possible to greatly shorten the working time ofthe whole timing calibration.

1. A method for calibrating a semiconductor test instrument forperforming timing calibration of a semiconductor test instrument havingdrivers for generating signals synchronizing with clock signals andcomparators for performing comparisons synchronizing with strobesignals, comprising: a first step of adjusting phases of one of saidclock signals and said strobe signals, both of which are set inone-to-one correspondence, on the basis of the other while each of saiddrivers corresponds to each of said comparators; a second step ofobtaining relative phase differences between said clock signalscorresponding to said drivers respectively or relative phase differencesbetween said strobe signals corresponding to said comparatorsrespectively; and a third step of adjusting phases of said clock signalsand phases of said strobe signals in accordance with said relative phasedifferences.
 2. The method for calibrating a semiconductor testinstrument according to claim 1, characterized in that the phaseadjustment to be executed in said first step is performed by varyingphases of said clock signals so that timings for performing comparisonsby said comparators in accordance with said strobe signals coincide withtimings at which signals output from said drivers and input to saidcomparators are changed.
 3. The method for calibrating a semiconductortest instrument according to claim 1, characterized in that the phaseadjustment to be executed in said first step is performed by varyingphases of said strobe signals so that timings for performing comparisonsby said comparators in accordance with said strobe signals coincide withtimings at which signals output from said drivers and input to saidcomparators are changed.
 4. The method for calibrating a semiconductortest instrument according to claim 1, characterized in that the phasedifference obtainment to be executed in said second step is performed bymeasuring phase differences of one of said clock signals and said strobesignals set in one-to-one correspondence on the basis of phasedifferences of the other while changing combinations of drivers withcomparators in the first step.
 5. The method for calibration asemiconductor test instrument according to claim 1, characterized inthat a delay element for varying the phase of a signal is inserted intoeach of supply routes of said clock signals to said drivers and each ofsupply routes of said strobe signals to said comparators.
 6. The methodfor calibrating a semiconductor test instrument according to claim 1,characterized in that said first step is executed by using a firstcalibration board on which the output end of corresponding one of saiddrivers and the input end of corresponding one of said comparators areconnected to each of a plurality of short connection points throughwirings having equal time lengths.
 7. The method for calibrating asemiconductor test instrument according to claim 6, characterized inthat said second step is executed by using a second calibration boarddifferent from said first calibration board in combination of wirings,in which the output end of corresponding one of said drivers and theinput end of corresponding one of said comparators are connected to eachof a plurality of short connection points through wirings having equaltime lengths.
 8. The method for calibrating a semiconductor testinstrument according to claim 7, characterized in that a fourth step ofexchanging said first calibration board with said second calibrationboard is included between said first step and said second step.
 9. Themethod for calibrating a semiconductor test instrument according toclaim 1, characterized in that said first step is executed by using athird calibration board in which the output end of corresponding one ofsaid drivers and the input end of corresponding one of said comparatorsare connected to each of a plurality of short connection points throughwirings having equal time lengths, and said second step is executed bychanging over wiring states of said third calibration board so that theoutput end of corresponding one of said drivers and the input end ofcorresponding one of said comparators are connected to each of aplurality of short connection points through wirings having equal timelengths.
 10. The method for calibrating a semiconductor test instrumentaccording to claim 9, characterized in that said third calibration boardincludes a plurality of changeover switches for changing over wiringstates and operations in said first and second steps are executed bychanging over connection states of these changeover switches.
 11. Themethod for calibrating a semiconductor test instrument according toclaim 1, characterized in that said first step is executed by using afirst calibration device in which the output end of corresponding one ofsaid drivers and the input end of corresponding one of said comparatorsare connected to each of a plurality of short connection points throughwirings having equal time lengths.
 12. The method for calibrating asemiconductor test instrument according to claim 11, characterized inthat said second step is executed by using a second calibration devicedifferent from said first calibration device in combination of wirings,in which the output end of corresponding one of said drivers and theinput end of corresponding one of said comparators are connected to eachof a plurality of short connection points through wirings having equaltime lengths.
 13. The method for calibrating a semiconductor testinstrument according to claim 12, characterized in that a fourth step ofexchanging said first calibration device with said second calibrationdevice by using a handler is included between said first step and saidsecond step.
 14. The method for calibrating a semiconductor testinstrument according to claim 1, characterized in that said first stepis executed by using a first region in a first calibration wafer inwhich the output end of corresponding one of said drivers and the inputend of corresponding one of said comparators are connected to each of aplurality of short connection points through wirings having equal timelengths, and said second step is executed by using a second region in asecond calibration wafer different from said first calibration wafer incombination of wirings, in which the output end of corresponding one ofsaid drivers and the input end of corresponding one of said comparatorsare connected to each of a plurality of short connection points throughwirings having equal lengths.
 15. The method for calibrating asemiconductor test instrument according to claim 14, characterized inthat said first calibration wafer and said second calibration wafer arethe same wafer and said first and second regions are formed in said samewafer.